text:
# Data Transformation

## Preface

After you have acquired the data, you should do the following:

• Diagnose data quality.
• If there is a problem with data quality,
• The data must be corrected or re-acquired.
• Explore data to understand the data and find scenarios for performing the analysis.
• Derive new variables or perform variable transformations.

The dlookr package makes these steps fast and easy:

• Performs an data diagnosis or automatically generates a data diagnosis report.
• Discover data in a variety of ways, and automatically generate EDA(exploratory data analysis) report.
• Imputate missing values and outliers, resolve skewed data, and binarize continuous variables into categorical variables. And generates an automated report to support it.

This document introduces data transformation methods provided by the dlookr package. You will learn how to transform of tbl_df data that inherits from data.frame and data.frame with functions provided by dlookr.

dlookr synergy with dplyr increases. Particularly in data transformation and data wrangle, it increases the efficiency of the tidyverse package group.

## datasets

To illustrate the basic use of EDA in the dlookr package, I use a Carseats datasets. Carseats in the ISLR package is simulation dataset that sells children’s car seats at 400 stores. This data is a data.frame created for the purpose of predicting sales volume.

library(ISLR)
str(Carseats)
'data.frame':   400 obs. of  11 variables:
$Sales : num 9.5 11.22 10.06 7.4 4.15 ...$ CompPrice  : num  138 111 113 117 141 124 115 136 132 132 ...
$Income : num 73 48 35 100 64 113 105 81 110 113 ...$ Advertising: num  11 16 10 4 3 13 0 15 0 0 ...
$Population : num 276 260 269 466 340 501 45 425 108 131 ...$ Price      : num  120 83 80 97 128 72 108 120 124 124 ...
$ShelveLoc : Factor w/ 3 levels "Bad","Good","Medium": 1 2 3 3 1 1 3 2 3 3 ...$ Age        : num  42 65 59 55 38 78 71 67 76 76 ...
$Education : num 17 10 12 14 13 16 15 10 10 17 ...$ Urban      : Factor w/ 2 levels "No","Yes": 2 2 2 2 2 1 2 2 1 1 ...
Sales_minmax = transform(carseats$Sales, method = "minmax")) %>% select(Income_minmax, Sales_minmax) %>% boxplot() ### Resolving Skewness data with transform() find_skewness() calculates the skewness and finds the skewed data. # find index of skewed variables find_skewness(carseats) [1] 4 # find names of skewed variables find_skewness(carseats, index = FALSE) [1] "Advertising" # compute the skewness find_skewness(carseats, value = TRUE) Sales CompPrice Income Advertising Population Price 0.185 -0.043 NA 0.637 -0.051 -0.125 Age Education -0.077 0.044 # compute the skewness & filtering with threshold find_skewness(carseats, value = TRUE, thres = 0.1) Sales Advertising Price 0.185 0.637 -0.125  The skewness of Advertising is 0.637, which is a little slanted to the left, so I use transformation () to convert it to log. summary() summarizes the transformation information, and plot() visualizes the transformation information. Advertising_log = transform(carseats$Advertising, method = "log")

# result of transformation
[1] 2.397895 2.772589 2.302585 1.386294 1.098612 2.564949
# summary of transformation
Warning: cols is now required.
Please use cols = c(statistic)
* Resolving Skewness with log

* Information of Transformation (before vs after)
Original Transformation
n        400.0000000    400.0000000
na         0.0000000      0.0000000
mean       6.6350000           -Inf
sd         6.6503642            NaN
se_mean    0.3325182            NaN
IQR       12.0000000            Inf
skewness   0.6395858            NaN
kurtosis  -0.5451178            NaN
p00        0.0000000           -Inf
p01        0.0000000           -Inf
p05        0.0000000           -Inf
p10        0.0000000           -Inf
p20        0.0000000           -Inf
p25        0.0000000           -Inf
p30        0.0000000           -Inf
p40        2.0000000      0.6931472
p50        5.0000000      1.6094379
p60        8.4000000      2.1265548
p70       11.0000000      2.3978953
p75       12.0000000      2.4849066
p80       13.0000000      2.5649494
p90       16.0000000      2.7725887
p95       19.0000000      2.9444390
p99       23.0100000      3.1359198
p100      29.0000000      3.3672958
# viz of transformation
plot(Advertising_log)

It seems that the raw data contains 0, as there is a -Inf in the log converted value. So this time we convert it to “log + 1”.

Advertising_log <- transform(carseats$Advertising, method = "log+1") # result of transformation head(Advertising_log) [1] 2.484907 2.833213 2.397895 1.609438 1.386294 2.639057 # summary of transformation summary(Advertising_log) Warning: cols is now required. Please use cols = c(statistic) * Resolving Skewness with log+1 * Information of Transformation (before vs after) Original Transformation n 400.0000000 400.00000000 na 0.0000000 0.00000000 mean 6.6350000 1.46247709 sd 6.6503642 1.19436323 se_mean 0.3325182 0.05971816 IQR 12.0000000 2.56494936 skewness 0.6395858 -0.19852549 kurtosis -0.5451178 -1.66342876 p00 0.0000000 0.00000000 p01 0.0000000 0.00000000 p05 0.0000000 0.00000000 p10 0.0000000 0.00000000 p20 0.0000000 0.00000000 p25 0.0000000 0.00000000 p30 0.0000000 0.00000000 p40 2.0000000 1.09861229 p50 5.0000000 1.79175947 p60 8.4000000 2.23936878 p70 11.0000000 2.48490665 p75 12.0000000 2.56494936 p80 13.0000000 2.63905733 p90 16.0000000 2.83321334 p95 19.0000000 2.99573227 p99 23.0100000 3.17846205 p100 29.0000000 3.40119738 # viz of transformation plot(Advertising_log) ## Binning ### Binning of individual variables using binning() binning() transforms a numeric variable into a categorical variable by binning it. The following types of binning are supported. • “quantile” : categorize using quantile to include the same frequencies • “equal” : categorize to have equal length segments • “pretty” : categorized into moderately good segments • “kmeans” : categorization using K-means clustering • “bclust” : categorization using bagged clustering technique The following example illustrates some ways to Income binning using binning().: # Binning the carat variable. default type argument is "quantile" bin <- binning(carseats$Income)
# Print bins class object
bin
binned type: quantile
number of bins: 10
x
[21,30]     (30,39]     (39,48]     (48,62]     (62,69]     (69,78]
40          37          38          40          42          33
(78,86.6] (86.6,96.6]  (96.6,109]   (109,120]        <NA>
36          38          39          37          20
# Summarise bins class object
summary(bin)
levels freq   rate
1      [21,30]   40 0.1000
2      (30,39]   37 0.0925
3      (39,48]   38 0.0950
4      (48,62]   40 0.1000
5      (62,69]   42 0.1050
6      (69,78]   33 0.0825
7    (78,86.6]   36 0.0900
8  (86.6,96.6]   38 0.0950
9   (96.6,109]   39 0.0975
10   (109,120]   37 0.0925
11        <NA>   20 0.0500
# Plot bins class object
plot(bin)

# Using labels argument
bin <- binning(carseats$Income, nbins = 4, labels = c("LQ1", "UQ1", "LQ3", "UQ3")) bin binned type: quantile number of bins: 4 x LQ1 UQ1 LQ3 UQ3 <NA> 95 102 89 94 20 # Using another type argument binning(carseats$Income, nbins = 5, type = "equal")
binned type: equal
number of bins: 5
x
[21,40.8] (40.8,60.6] (60.6,80.4]  (80.4,100]   (100,120]        <NA>
81          65          94          80          60          20
binning(carseats$Income, nbins = 5, type = "pretty") binned type: pretty number of bins: 5 x [20,40] (40,60] (60,80] (80,100] (100,120] <NA> 81 65 94 80 60 20 binning(carseats$Income, nbins = 5, type = "kmeans")
binned type: kmeans
number of bins: 5
x
[21,49]   (49,70.5] (70.5,86.5]  (86.5,104]   (104,120]        <NA>
115          86          65          65          49          20
binning(carseats$Income, nbins = 5, type = "bclust") binned type: bclust number of bins: 5 x [21,46.5] (46.5,64.5] (64.5,78.5] (78.5,95.5] (95.5,120] <NA> 109 58 63 71 79 20 # ------------------------- # Using pipes & dplyr # ------------------------- library(dplyr) carseats %>% mutate(Income_bin = binning(carseats$Income)) %>%
group_by(ShelveLoc, Income_bin) %>%
summarise(freq = n()) %>%
arrange(desc(freq)) %>%
Warning: Factor Income_bin contains implicit NA, consider using
forcats::fct_explicit_na
# A tibble: 10 x 3
# Groups:   ShelveLoc [1]
ShelveLoc Income_bin  freq
<fct>     <ord>      <int>
1 Medium    [21,30]       25
2 Medium    (62,69]       24
3 Medium    (48,62]       23
4 Medium    (39,48]       21
# … with 6 more rows

### Optimal Binning with binning_by()

binning_by() converts a numeric variable into a categorical variable by optimal binning. This method is often used when developing a scorecard model.

The following binning_by() example optimally binning Advertising if US is a target variable with a binary class.

# optimal binning
Warning in binning_by(carseats, "US", "Advertising"): The factor y has been
changed to a numeric vector consisting of 0 and 1.
bin
binned type: optimal
number of bins: 3
x
[-1,0]  (0,6] (6,29]
144     69    187

# summary optimal_bins class
summary(bin)
levels freq   rate
1 [-1,0]  144 0.3600
2  (0,6]   69 0.1725
3 (6,29]  187 0.4675

# information value
attr(bin, "iv")
[1] 4.8349

# information value table
attr(bin, "ivtable")
1     <= 0    144      19    125       144         19       125 0.3600   0.1319
2     <= 6     69      54     15       213         73       140 0.1725   0.7826
3      > 6    187     185      2       400        258       142 0.4675   0.9893
4  Missing      0       0      0       400        258       142 0.0000      NaN
5    Total    400     258    142        NA         NA        NA 1.0000   0.6450
1  0.8681  0.1520 -1.8839 -2.4810 2.0013
2  0.2174  3.6000  1.2809  0.6838 0.0709
3  0.0107 92.5000  4.5272  3.9301 2.7627
4     NaN     NaN     NaN     NaN    NaN
5  0.3550  1.8169  0.5971  0.0000 4.8349

# visualize optimal_bins class
plot(bin, sub = "bins of Advertising variable")

## Creating a data transformation report using transformation_report()

transformation_report() creates a data transformation report for all the variables in the data frame or objects that inherit the data frame (tbl_df, tbl, etc.).

transformation_report() creates a data transformation report in two forms:

• pdf file based on Latex
• html file

The contents of the report are as follows.:

• Imputation
• Missing Values
• Missing values imputation information
• (variable names)
• Outliers
• Outliers imputation information
• (variable names)
• Resolving Skewness
• Skewed variables information
• (variable names)
• Binning
• Numerical Variables for Binning
• Binning
• (variable names)
• Optimal Binning
• (variable names)

The following creates a data transformation report for carseats. The file format is pdf, and the file name is Transformation_Report.pdf.

carseats %>%
transformation_report(target = US)

The following generates a report in html format called transformation.html.

carseats %>%
transformation_report(target = US, output_format = "html",
output_file = "transformation.html")

Data transformation reports are automated reports to assist in the data transformation process. Design data conversion scenarios by referring to the report results.

### Data transformation report contents

#### Contents of pdf file

• The cover of the report is shown in the following figure.
• The report’s argenda is shown in the following figure.
• Much of the information is displayed in tables and visualization results in reports. An example is shown in the following figure.

#### Contents of html file

• The title and contents of the report are shown in the following figure.
• Much information is represented in tables in the report. An example of a table in an html file is shown in the following figure.
• Binning information in the data transformation report includes visualization results. The result of the html file is shown in the following figure.


text:
# Questions & Answers of Regular and Contex-Free Languages, Pumping Lemma

If G is a grammar with productions

$\style{font-family:'Times New Roman'}{S\rightarrow SaS\;\vert\;aSb\;\vert\;bSa\;\vert\;SS\;\vert\;\in}$

where S is the start variable, then which one of the following strings is not generated by G?

Consider the following languages over the alphabet $\style{font-family:'Times New Roman'}{\sum=\{a,b,c\}.}$

Let $\style{font-family:'Times New Roman'}{L_1=\{a^nb^nc^m\vert m,n\geq0\}\;and\;\;L_2=\{a^mb^nc^n\vert m,n\geq0\}.}$

Which of the following are context-free languages?

$\style{font-family:'Times New Roman'}{\begin{array}{l}\mathrm I.\;\;\;\;{\mathrm L}_1\cup\;{\mathrm L}_2\\\mathrm{II}.\;\;{\mathrm L}_1\cap\;{\mathrm L}_2\end{array}}$

Which one of the following regular expressions represents the language: the set of all binary strings having two consecutive 0s and two consecutive 1s?

Language L1 is defined by the grammar:

Language L2 is defined by the grammar:

Consider the following statements:

P: L1 is regular

Q: L2 is regular

Which one of the following is TRUE?

III.${L}_{1}^{*}\cap {L}_{2}$ is context-free
IV.${L}_{1}\cup \overline{{L}_{2}}$ is context-free

format: plain


text:
Vector Calculus - Tensor Identity Problem

Tags:
1. Dec 7, 2016

mille2eo

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

I am really lost here because our professor gave us no example problems leading up to the final exam and now we are expected to understand everything about vector calculus.

This is my attempt at the cross product and dot product written out. I don't know how to proceed to make the left hand side equal the right hand side.

2. Dec 7, 2016

eys_physics

Use the expression for the scalar product between two vectors $\mathbf{a}$ and $\mathbf{b}$:
$$\mathbf{a}\cdot\mathbf{b}=\sum_i a_i b_i$$


text:
## The loop macro in emacs lisp

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I was reading The Land Of Lisp chapter on the loop macro in Common Lisp. I am not too familiar with it, or the implementation in emacs-lisp, so in this post we explore what it can do. Here I will explore some uses of the loop macro to do things I used to do in Python all the time.

Here is a simple example to generate a list of numbers with the loop macro..

(loop for i
below 5
collect i)

 0 1 2 3 4

Evidently, i starts at 0, and increments by one. We can specify a different value like this. Here we use the to token, which also includes the last value.

(loop for i from 2 to 10
collect i)

 2 3 4 5 6 7 8 9 10

IF you want to go backwards:

(loop for i downfrom 10 to 2 collect i)

 10 9 8 7 6 5 4 3 2

And if you want an (de)increment different than one, use the by token.

(loop for i downfrom 10 to 2 by 3 collect i)

 10 7 4

We can use this to iterate over a list too. Let us collect the square of each element in a simple list. This is similar to the mapcar function.

(loop for i in '(1 2 3 4)
collect (* i i))

 1 4 9 16

You can combine the ideas to get something similar to the enumerate function in python.

(loop for i
from 0
for month
in '(january february march april may june july august september
october november december)
collect (cons i month))

((0 . january)
(1 . february)
(2 . march)
(3 . april)
(4 . may)
(5 . june)
(6 . july)
(7 . august)
(8 . september)
(9 . october)
(10 . november)
(11 . december))

The loop stops because we run out of months to iterate over. Here is a variation like the zip function in python.

(loop for element1 in '(a b c d)
for element2 in '(1 2 3 4)
collect (list element1 element2))

 a 1 b 2 c 3 d 4

We can sum in the loop:

(loop for i in '(100 200 300) sum i)

600

We can conditionally sum things in the loop, e.g. sum only the odd numbers.

(loop for i in '(1 2 3 4 5)
when (oddp i)
sum i)

9

We can find the minima and maxima in a list

(loop for i in '(-1 0 1)
minimize i)

-1

(loop for i in '(-1 0 1)
maximize i)

1

You may want to do some action in the loop. Say we want to print even numbers from a list.

(loop for i in '(1 2 3 4)
when (evenp i)
do (print i))

2

4

There are some ways to break out of a loop using return like this.

(loop for i upto 10
when (= i 3)
return 'done
do (print i))

0

1

2

Alternatively, you can use while/until.

(loop for i downfrom 10
do (print i)
until (= i 6))

10

9

8

7

6

Or the while variation:

(loop for i downfrom 10
do (print i)
while (> i 6))

10

9

8

7

6

## 1 Summary

This is not everything the loop macro can do! Here is what the help for that function says.

loop is an alias for cl-loop' in cl.el'.

(loop CLAUSE...)

The Common Lisp loop' macro.
Valid clauses include:
For clauses:
for VAR from/upfrom/downfrom EXPR1 to/upto/downto/above/below EXPR2 by EXPR3
for VAR = EXPR1 then EXPR2
for VAR in/on/in-ref LIST by FUNC
for VAR across/across-ref ARRAY
for VAR being:
the elements of/of-ref SEQUENCE [using (index VAR2)]
the symbols [of OBARRAY]
the hash-keys/hash-values of HASH-TABLE [using (hash-values/hash-keys V2)]
the key-codes/key-bindings/key-seqs of KEYMAP [using (key-bindings VAR2)]
the overlays/intervals [of BUFFER] [from POS1] [to POS2]
the frames/buffers
the windows [of FRAME]
Iteration clauses:
repeat INTEGER
while/until/always/never/thereis CONDITION
Accumulation clauses:
collect/append/nconc/concat/vconcat/count/sum/maximize/minimize FORM
[into VAR]
Miscellaneous clauses:
with VAR = INIT
if/when/unless COND CLAUSE [and CLAUSE]... else CLAUSE [and CLAUSE...]
named NAME
initially/finally [do] EXPRS...
do EXPRS...
[finally] return EXPR

For more details, see Info node (cl)Loop Facility'.

It is obviously quite powerful, although the syntax seems quite different than the usual lisp code I have been writing. It is not clear when this is superior to something like mapcar/mapconcat, or the dolist/dotimes functions.

org-mode source

Org-mode version = 8.2.7c

## Generate emacs-lisp documentation

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Emacs has some pretty amazing features to get help on a function (describe-function), to navigate quickly to functions in an elisp file (speedbar and imenu). Other languages have tools for generating documentation for all the functions in a file, e.g. epydoc, javadoc, Doxygen,… I have not found an equivalent to this in emacs-lisp. Here, we explore some options to get something similar to this. Our goal will be to take an emacs-lisp file, and generate an org-file of documentation, and then convert that to PDF for reading.

Say we have a function, jmax-bibtex-next-entry, and we want some information about it. Here are three functions that give us the argument list, documentation string, and function definition.

(help-function-arglist 'jmax-bibtex-next-entry)

 &optional n
(documentation 'jmax-bibtex-next-entry)

Jump to the beginning of the next bibtex entry. N is a prefix
argument. If it is numeric, jump that many entries
forward. Negative numbers do nothing.

(symbol-function 'jmax-bibtex-next-entry)

 lambda (&optional n) Jump to the beginning of the next bibtex entry. N is a prefix\nargument. If it is numeric, jump that many entries\nforward. Negative numbers do nothing. (interactive P) (if (= (point) (save-excursion (bibtex-beginning-of-entry))) (progn (forward-char) (bibtex-next-entry))) (if (re-search-forward bibtex-entry-head nil t (and (numberp n) n)) (progn (bibtex-beginning-of-entry)))

That will not always be the code we wrote, but it is functionally similar.

So we could create an org-entry like this:

(defun fun2org (function-symbol)
(let ((args (help-function-arglist function-symbol))
(doc  (documentation function-symbol))
(code (symbol-function function-symbol)))
(format "** %s %s
%s

#+BEGIN_SRC emacs-lisp
%S
#+END_SRC
" function-symbol args doc code)))

(fun2org 'jmax-bibtex-next-entry)

** jmax-bibtex-next-entry (&optional n)
Jump to the beginning of the next bibtex entry. N is a prefix
argument. If it is numeric, jump that many entries
forward. Negative numbers do nothing.

#+BEGIN_SRC emacs-lisp
(lambda (&optional n) "Jump to the beginning of the next bibtex entry. N is a prefix
argument. If it is numeric, jump that many entries
forward. Negative numbers do nothing." (interactive "P") (if (= (point) (save-excursion (bibtex-beginning-of-entry))) (progn (forward-char) (bibtex-next-entry))) (if (re-search-forward bibtex-entry-head nil t (and (numberp n) n)) (progn (bibtex-beginning-of-entry))))
#+END_SRC

The code is not that beautifully indented, but it is optional.

For variables, there are similar functions to get their documentation:

(documentation-property 'jmax-bibtex-journal-abbreviations 'variable-documentation)

List of (string journal-full-name journal-abbreviation). Find abbreviations at http://cassi.cas.org/search.jsp.

The problem still is, you have to know the variable and function names in advance. I want to take a file, and generate this for each function, and variable.

I posted a question on StackOverflow on how to get the functions defined in a file. The most feasible suggestion was to use the variable load-history, which contains a history of the variables and functions loaded, and the files they are in.

Here is an example of getting the entries associated with jmax-bibtex.el

(cdr (assoc "/Users/jkitchin/Dropbox/kitchingroup/jmax/jmax-bibtex.el" load-history ))

(jmax-bibtex-journal-abbreviations
(defun . jmax-bibtex-generate-longtitles)
(defun . jmax-bibtex-generate-shorttitles)
(defun . jmax-stringify-journal-name)
(defun . jmax-set-journal-string)
jmax-nonascii-latex-replacements
(defun . jmax-replace-nonascii)
jmax-lower-case-words
(defun . jmax-title-case-article)
(defun . jmax-sentence-case-article)
(defun . jmax-bibtex-next-entry)
(defun . jmax-bibtex-previous-entry)
(defun . jmax-bibtex-mode-keys)
(provide . jmax-bibtex))

Each element in this case is either a variable, defun or provide. Here, we can use this to print some information about the variables defined in this file. I think it is sufficient to check if the element in the list is a symbol, because all the other elements are cons elements. I suppose there are other possibilities, including defcustom, defgroup, defalias, defsubst, and maybe others.

(dolist (element (cdr
(assoc
"/Users/jkitchin/Dropbox/kitchingroup/jmax/jmax-bibtex.el"
(when (symbolp element)
(princ
(format "%s
Documentation: %s

" element (documentation-property element 'variable-documentation)))))

jmax-bibtex-journal-abbreviations
Documentation: List of (string journal-full-name journal-abbreviation). Find abbreviations at http://cassi.cas.org/search.jsp.

jmax-nonascii-latex-replacements
Documentation: Cons list of non-ascii characters and their LaTeX representations

jmax-lower-case-words
Documentation: List of words to keep lowercase

We can handle functions by checking if an element is a cons cell with a first element of defun.

(dolist (element (cdr
(assoc
"/Users/jkitchin/Dropbox/kitchingroup/jmax/jmax-bibtex.el"
(when (and (consp element)
(eq (car element) 'defun))
(princ (format "%s is a function\n" (cdr element))))))

jmax-bibtex-generate-longtitles is a function
jmax-bibtex-generate-shorttitles is a function
jmax-stringify-journal-name is a function
jmax-set-journal-string is a function
jmax-replace-nonascii is a function
jmax-title-case-article is a function
jmax-sentence-case-article is a function
jmax-bibtex-next-entry is a function
jmax-bibtex-previous-entry is a function
jmax-bibtex-mode-keys is a function

So, we have the important pieces to mash up what I am looking for. Let us refine the goal. I want to create a PDF documentation of what is in an elisp file with a section on variables, and a section on functions.

(let* ((elements (cdr
(assoc
"/Users/jkitchin/Dropbox/kitchingroup/jmax/jmax-bibtex.el"
(vars (-filter 'symbolp elements))
(funcons (-filter (lambda (x)
(and (consp x)
(eq 'defun (car x))))
elements))
(funcs (mapcar 'cdr funcons)))
(switch-to-buffer "*org-doc*")
(erase-buffer)
(insert (format "#+TITLE: Documentation for %s
#+OPTIONS: toc:nil
\\maketitle
\\tableofcontents
" "/Users/jkitchin/Dropbox/kitchingroup/jmax/jmax-bibtex.el"))
(insert "* Variables\n")
(dolist (var (sort vars 'string-lessp))
(insert (format "** %s
Documentation: %s\n\n" var  (documentation-property var 'variable-documentation))))

(insert "* Functions\n\n")
(dolist (funcs (sort funcs 'string-lessp))
(insert (format "** %s %s
Documentation: %s

Code:
#+BEGIN_SRC emacs-lisp
%S
#+END_SRC
"
funcs
(or (help-function-arglist funcs) "")
(documentation funcs)
(symbol-function funcs))))

(org-mode)
(write-file "jmax-bibtex-doc.org")
(org-export-to-file 'latex "jmax-bibtex-doc.tex")
(org-latex-compile "jmax-bibtex-doc.tex")
(kill-buffer "*org-doc*")
(kill-buffer "jmax-bibtex-doc.org"))

Here is the resulting pdf: jmax-bibtex-doc.pdf . It is not too bad. The code is not beautiful, and it would take some work to get that looking nice. It might be nice to find all instances of ' and replace them with links to variable names, but I leave that for another day. There is also no information about the header comments, but I leave this for another day to.

org-mode source

Org-mode version = 8.2.7c

## Randomize a list in Emacs

| categories: emacs_lisp | tags: | View Comments

I have an application where I have a list of userids, and I want to randomize the order of the list. Today, I explore some ways to do that. The first idea is to simply mimic the algorithm in Python's random.shuffle algorithm.

    def shuffle(self, x, random=None):
"""x, random=random.random -> shuffle list x in place; return None.

Optional arg random is a 0-argument function returning a random
float in [0.0, 1.0); by default, the standard random.random.

"""

if random is None:
random = self.random
_int = int
for i in reversed(xrange(1, len(x))):
# pick an element in x[:i+1] with which to exchange x[i]
j = _int(random() * (i+1))
x[i], x[j] = x[j], x[i]

It looks like we loop through the elements, and swap them at random.

We have a similar feature for xrange in emacs-lisp:

(number-sequence 1 5)

 1 2 3 4 5

Note that number-sequence includes the last value, unlike xrange. And for reverse:

(reverse (number-sequence 1 5))

 5 4 3 2 1

Of course, we can select random numbers:

(random 5) ; random between 0 and 5

4

Last, we need to work out how to swap to elements. It looks like this will swap elements 2 and 3. We store element 3 temporarily, set 3 to 2, and then set 2 to the temporarily stored value of 3.

(let* ((L '(1 2 3 4))
(tmp (nth 3 L)))
(setf (nth 3 L) (nth 2 L))
(setf (nth 2 L) tmp)
L)

 1 2 4 3

So, now we can shuffle our list.

(setq userids '(user1 user2 user3 user4 user5 user6))

(defun swap (LIST el1 el2)
"in LIST swap indices EL1 and EL2 in place"
(let ((tmp (nth el1 LIST)))
(setf (nth el1 LIST) (nth el2 LIST))
(setf (nth el2 LIST) tmp)))

;; now run the loop
(loop for i in (reverse (number-sequence 1 (1- (length userids))))
do (let ((j (random (+ i 1))))
(swap userids i j)))

userids

 user4 user6 user3 user2 user1 user5

The order has certainly changed. It is a little difficult to tell how randomized it actually is, but what is important for my application is that the order is different each time I use it. It looks like this will accomplish that objective. I think this basically implements the algorithm in the Python random.shuffle code. That code does something a little differently. It generates a random float between 0-1, multiplies it by i + 1, and converts the result to an integer. We directly get an integer in the range of 0 to i + 1. I think the result is practically the same.

Finally, let us wrap the whole thing up in a nice neat function for future use. We will use elt instead of nth so it works for arrays too.

(defun swap (LIST el1 el2)
"in LIST swap indices EL1 and EL2 in place"
(let ((tmp (elt LIST el1)))
(setf (elt LIST el1) (elt LIST el2))
(setf (elt LIST el2) tmp)))

(defun shuffle (LIST)
"Shuffle the elements in LIST.
shuffling is done in place."
(loop for i in (reverse (number-sequence 1 (1- (length LIST))))
do (let ((j (random (+ i 1))))
(swap LIST i j)))
LIST)

shuffle

Example usage for a list:

(shuffle '(user1 user2 user3 user4 user5 user6))

 user4 user2 user3 user5 user6 user1

And for a vector:

(shuffle [user1 user2 user3 user4 user5 user6])

[user3 user2 user6 user4 user5 user1]

Artur at http://endlessparentheses.com suggested one can use psetf to swap values. Thanks for the tip, I was not aware of that cool function. It evaluates the values first, then sets them, so there is no need for a temporary storage of a value! Here is an example usage. We could rewrite our swap function like this if we wanted.

(let ((LIST '(1 2 3 4 5)))
(psetf (elt LIST 2) (elt LIST 1)
(elt LIST 1) (elt LIST 2))
LIST)
`
 1 3 2 4 5


text:
# chemtools.wrappers.molecule.Molecule¶

class chemtools.wrappers.molecule.Molecule(iodata)[source]

Molecule class from HORTON package.

Initialize class.

Parameters: iodata (horton.IOData) – An instance of horton.IOData object.
classmethod from_file(fname)[source]

Initialize class given a file.

Parameters: fname (str) – Path to molecule”s files.
coordinates

Cartesian coordinates of atomic centers.

numbers

Atomic number of atomic centers.

ao

Atomic orbital instance.

mo

Molecular orbital instance.

compute_density_matrix(spin='ab', index=None)[source]

Compute the density matrix array for the specified spin orbitals.

Parameters: spin (str, optional) – The type of occupied spin orbitals. Options are “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.
compute_molecular_orbital(points, spin='ab', index=None)[source]

Return molecular orbitals.

Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.
compute_density(points, spin='ab', index=None)[source]

Return electron density.

Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.

Return gradient of the electron density.

Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.
compute_hessian(points, spin='ab', index=None)[source]

Return hessian of the electron density.

Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.
compute_laplacian(points, spin='ab', index=None)[source]

Return Laplacian of the electron density.

Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.
compute_esp(points, spin='ab', index=None, charges=None)[source]

Return molecular electrostatic potential.

The molecular electrostatic potential at point $$\mathbf{r}$$ is caused by the electron density $$\rho$$ of the specified spin orbitals and set of point charges $$\{q_A\}_{A=1}^{N_\text{atoms}}$$ placed at the position of the nuclei. i.e,

$V \left(\mathbf{r}\right) = \sum_{A=1}^{N_\text{atoms}} \frac{q_A}{\rvert \mathbf{R}_A - \mathbf{r} \lvert} - \int \frac{\rho \left(\mathbf{r}"\right)}{\rvert \mathbf{r}" - \mathbf{r} \lvert} d\mathbf{r}"$
Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included. charges (np.ndarray, optional) – Array with shape (n,) representing the point charges at the position of the nuclei. When None, the pseudo numbers are used.
compute_ked(points, spin='ab', index=None)[source]

Return positive definite or Lagrangian kinetic energy density.

$\tau_\text{PD} \left(\mathbf{r}\right) = \tfrac{1}{2} \sum_i^N n_i \rvert \nabla \phi_i \left(\mathbf{r}\right) \lvert^2$
Parameters: points (ndarray) – Cartesian coordinates of N points given as a 2D-array with (N, 3) shape. spin (str, optional) – Type of occupied spin orbitals which can be either “a” (for alpha), “b” (for beta), and “ab” (for alpha + beta). index (sequence of int, optional) – Sequence of integers representing the occupied spin orbitals which are indexed from 1 to nbasis. If None, all orbitals of the given spin(s) are included.


text:
# A Diophantine Problem

• March 22nd 2008, 04:13 AM
enrique
A Diophantine Problem
What is the general solution of x^4 + y^2 = z^2 ?

We know that primitive Pythagorean triples correspond to the triples (2st, s^2 - t^2, s^2 + t^2), where gcd (s,t)=1. So i separate the problem into two cases:

i) x is even : i found the general solution as
(sqrt(2st), s^2 - t^2, s^2 + t^2).

ii) y is even : i found the general solution as
(sqrt(s^2 - t^2), 2st, s^2 + t^2).

Is this solution true? Or in other words, do these triples produce every solution of this equation?
• March 22nd 2008, 07:14 PM
ThePerfectHacker
Case 1: x is even. Then we know $x^2 = 2st , y = s^2 - t^2, z=s^2+t^2$ where $\gcd(s,t)=1$ and the parity is different. It is safe to assume that $s$ is even (because the other way around everything is symettric except for $y$ but that not matter because we are squaring it, and thereby removing the negative sign). But $x=2x'$. Which means, $4(x')^2 = 2st \implies (x')^2 = (s/2)t$ (remember $s$ is even). Since $\gcd(s/2,t)=1$ it means $s/2=a^2\implies s = 2a^2$ and $t=b^2$. Thus, $x=2ab, y=4a^2 - b^2, z=4a^2+b^2$. For arbitrary relatively prime integers $a,b$.

Case 2: x is odd. Then we know $x^2 = s^2 - t^2, y=2st, z=s^2+t^2$. Thus, $x^2 + t^2 = s^2$. This forces $t$ to be even. And so, $x=a^2 - b^2, t=2ab, s=a^2+b^2$. Thus, $x=a^2-b^2, y=4ab(a^2+b^2), z=(a^2+b^2) + 4a^2b^2$.
• March 23rd 2008, 08:26 AM
enrique
Thanks for the help ThePerfectHacker. Can we use the same strategy for the equations x^n + y^2 = z^2, where n>2? Or for which n we can apply the same procedure?

Note: I have noticed a small typo in the solution:z must be (a^2 + b^2)^2 + 4*((ab)^2).
• March 23rd 2008, 09:44 AM
ThePerfectHacker
Quote:

Originally Posted by enrique
Thanks for the help ThePerfectHacker. Can we use the same strategy for the equations x^n + y^2 = z^2, where n>2? Or for which n we can apply the same procedure?

I do not think so. Maybe if $n$ is a power of two.


text:
# Q.4 Look at the figures and write ’<’, or ’>’ ’=’ between the given pairs of fractions. (a) $$\frac{1}{6} \square \frac{1}{3}$$ (b) $$\frac{3}{4} \square \frac{2}{6}$$ (c) $$\frac{2}{3} \square \frac{2}{4}$$ (d) $$\frac{6}{6} \square \frac{3}{3}$$ (e) $$\frac{5}{6} \square \frac{5}{5}$$

(a) $$\frac{1}{6} < \frac{1}{3}$$
(b) $$\frac{3}{4} > \frac{2}{6}$$
(c) $$\frac{2}{3} > \frac{2}{4}$$
(d) $$\frac{6}{6} = \frac{3}{3}$$
(e) $$\frac{5}{6} < \frac{5}{5}$$


text:
# Fully Dynamic Betweenness Centrality

@inproceedings{Pontecorvi2015FullyDB,
title={Fully Dynamic Betweenness Centrality},
author={Matteo Pontecorvi and Vijaya Ramachandran},
booktitle={ISAAC},
year={2015}
}
• Published in ISAAC 9 December 2015
• Computer Science
We present fully dynamic algorithms for maintaining betweenness centrality (BC) of vertices in a directed graph $$G=(V,E)$$ with positive edge weights. BC is a widely used parameter in the analysis of large complex networks. We achieve an amortized $$O({\nu ^*}^2 \cdot \log ^3 n)$$ time per update with our basic algorithm, and $$O({\nu ^*}^2 \cdot \log ^2 n)$$ time with a more complex algorithm, where $$n = |V|$$, and $${\nu ^*}$$ bounds the number of distinct edges that lie on shortest paths…
13 Citations
A Faster Algorithm for Fully Dynamic Betweenness Centrality
• Computer Science, Mathematics
ArXiv
• 2015
This result improves on the amortized bound for fully dynamic BC in [Pontecorvi-Ramachandran2015] by a logarithmic factor and matches the fully dynamic APSP bound in Thorup for APSP in graphs with unique shortest paths.
Parallel Algorithm for Incremental Betweenness Centrality on Large Graphs
• Computer Science
IEEE Transactions on Parallel and Distributed Systems
• 2018
The serial implementation of the novel incremental algorithm, which decompose the graph into biconnected components and proves that processing can be localized within the affected components, is demonstrated to be up to 3.7 times faster than existing serial methods.
Temporal betweenness centrality in dynamic graphs
• Computer Science
International Journal of Data Science and Analytics
• 2019
The bi-objective notion of shortest–fastest path (SFP) in temporal graphs is proposed, which considers both space and time as a linear combination governed by a parameter, and a novel temporal betweenness centrality (TBC) metric is defined that outperforms static BC in the task of identifying the best vertices for propagating information.
• Computer Science
ACM J. Exp. Algorithmics
• 2018
This article considers the problem of determining how much a vertex can increase its centrality by creating a limited amount of new edges incident to it and proposes a simple greedy approximation algorithm for MBI with an almost tight approximation ratio and test its performance on several real-world networks.
Hierarchical Decomposition for Betweenness Centrality Measure of Complex Networks
• Computer Science
Scientific reports
• 2017
This work proposes a new hierarchical decomposition approach to speed up the betweenness computation of complex networks, and features a parallel structure, which is very suitable for parallel computation.
ABRA: Approximating Betweenness Centrality in Static and Dynamic Graphs with Rademacher Averages
• Computer Science
KDD
• 2016
We present ABRA, a suite of algorithms to compute and maintain probabilistically-guaranteed, high-quality, approximations of the betweenness centrality of all nodes (or edges) on both static and
Algorithms and Frameworks for Graph Analytics at Scale
This thesis presents a linear-space parallel incremental algorithm for updating betweenness centrality in large evolving graphs, which is up to an order of magnitude faster than the state-of-the-art parallel incremental algorithms.
Bavarian: Betweenness Centrality Approximation with Variance-Aware Rademacher Averages
• Computer Science, Mathematics
KDD
• 2021
Bavarian, a collection of sampling-based algorithms for approximating the Betweenness Centrality of all vertices in a graph, is presented and it is proved that, for all estimators, the sample size sufficient to achieve a desired approximation guarantee depends on the vertex-diameter of the graph, an easy-to-bound characteristic quantity.
Centrality Measures: A Tool to Identify Key Actors in Social Networks
• R. Singh
• Computer Science
Principles of Social Networking
• 2021
This chapter summarizes some of the centrality measures that are extensively applied for mining social network data and discusses various directions of research related to these measures.
Recent Advances in Fully Dynamic Graph Algorithms
• Computer Science
ArXiv
• 2021
A quick reference guide to recent engineering and theory results in the area of fully dynamic graph algorithms.

## References

SHOWING 1-10 OF 30 REFERENCES
A Faster Algorithm for Fully Dynamic Betweenness Centrality
• Computer Science, Mathematics
ArXiv
• 2015
This result improves on the amortized bound for fully dynamic BC in [Pontecorvi-Ramachandran2015] by a logarithmic factor and matches the fully dynamic APSP bound in Thorup for APSP in graphs with unique shortest paths.
Decremental All-Pairs ALL Shortest Paths and Betweenness Centrality
• Computer Science, Mathematics
ISAAC
• 2014
For graphs with a constant number of shortest paths between any pair of vertices, the algorithm maintains APASP and BC scores in amortized time $$O(n^2 \cdot \log n)$$ under decremental updates, regardless of the number of edges in the graph.
Approximating Betweenness Centrality
• Computer Science
WAW
• 2007
This paper presents a novel approximation algorithm for computing betweenness centrality of a given vertex, for both weighted and unweighted graphs, based on an adaptive sampling technique that significantly reduces the number of single-source shortest path computations for vertices with high centrality.
Betweenness Centrality - Incremental and Faster
• Computer Science
MFCS
• 2014
We present an incremental algorithm that updates the betweenness centrality (BC) score of all vertices in a graph G when a new edge is added to G, or the weight of an existing edge is reduced. Our
Fully-Dynamic All-Pairs Shortest Paths: Faster and Allowing Negative Cycles
We present a solution to the fully-dynamic all pairs shortest path problem for a directed graph with arbitrary weights allowing negative cycles. We support each vertex update in \(O(n^2({\rm log} n +
A Fast Algorithm for Streaming Betweenness Centrality
• Computer Science
2012 International Conference on Privacy, Security, Risk and Trust and 2012 International Confernece on Social Computing
• 2012
This work gives a novel algorithm that reduces computation for the insertion of an edge into the graph, the first algorithm for the computation of betweenness centrality in a streaming graph.
Scalable Online Betweenness Centrality in Evolving Graphs
• Computer Science
IEEE Transactions on Knowledge and Data Engineering
• 2015
This paper proposes the first truly scalable algorithm for online computation of betweenness centrality of both vertices and edges in an evolving graph where new edges are added and existing edges are removed and is carefully engineered with out-of-core techniques and tailored for modern parallel stream processing engines that run on clusters of shared-nothing commodity hardware.
Approximating Betweenness Centrality in Large Evolving Networks
• Computer Science
ALENEX
• 2015
The experimental study shows that the algorithms proposed are the first to make in-memory computation of a betweenness ranking practical for million-edge semi-dynamic networks and the accuracy is even better than the theoretical guarantees in terms of absolutes errors and the rank of nodes is well preserved.
QUBE: a quick algorithm for updating betweenness centrality
• Computer Science
WWW
• 2012
This work proposes a method that efficiently reduces the search space by finding a candidate set of vertices whose betweenness centralities can be updated and computes their betweenness centeralities using candidate vertices only.
A faster algorithm for betweenness centrality
New algorithms for betweenness are introduced in this paper and require O(n + m) space and run in O(nm) and O( nm + n2 log n) time on unweighted and weighted networks, respectively, where m is the number of links.


text:
# Electronics/AC Voltage and Current

## Relationship between Voltage and CurrentEdit

### ResistorEdit

In a resistor, the current is in phase with the voltage always. This means that the peaks and valleys of the two waveforms occur at the same times. Resistors can simply be defined as devices that perform the sole function of inhibiting the flow of current through an electrical circuit. Resistors are commercially available having various standard values, nevertheless variable resistors are also made called potentiometers, or pots for short. In theory electricity is a method used to harness myriad numbers including symbols to give the notion on how circuits function on a schematic drawing

### CapacitorEdit

The capacitor is different from the resistor in several ways. First, it consumes no real power. It does however, supply reactive power to the circuit. In a capacitor, as voltage is increasing the capacitor is charging. Thus a large initial current. As the voltage peaks the capacitor is saturated and the current falls to zero. Following the peak the circuit reverses and the charge leaves the capacitor. The next half of the cycle the circuit runs mirroring the first half.

The relationship between voltage and current in a capacitor is: ${\displaystyle i(t)=C{d(v(t)) \over dt}}$ . This is valid not only in AC but for any function v(t). As a direct consequence we can state that in the real world, the voltage across a capacitor is always a continuous function of the time.

If we apply the above formula to a AC voltage (i.e. ${\displaystyle v(t)=V\cdot sin(\omega t+\Phi )}$ ), we get for the current a 90° phase shift: ${\displaystyle i(t)=V\cdot \omega \cdot cos(\omega t+\Phi )}$ .

In an AC circuit, current leads voltage by a quarter phase or 90 degrees. Note that while in DC circuits after the initial charge or discharge no current can flow, in AC circuits a current flows all the time into and out of the capacitor, depending on the impedance in the circuit. This is similar to the resistance in DC circuits, except that the impedance has 2 parts; the resistance included in the circuit, and also the reactance of the capacitor, which depends not only on the size of the capacitor, but also on the frequency of the applied voltage. In a circuit that has DC applied plus a signal, a capacitor can be used to block the DC, while letting the signal continue.

### InductorEdit

In inductors, current is the negative derivative of voltage, meaning that however the voltage changes the current tries to oppose that change. When the voltage is not changing there is no current and no magnetic field.

In an AC Circuit, voltage leads current by a quarter phase or 90 degrees.

Voltage Defined as the derivative of the flux linkage:

${\displaystyle V(t)={d(Ni(t)) \over dt}}$

## ResonanceEdit

A circuit containing resistors, capacitors, and inductors is said to be in resonance when the reactance of the inductor cancels that of the capacitor to leave the resulting total resistance of the circuit to be equal to the value of the component resistor. The resonance state is achieved by fine tuning the frequency of the circuit to a value where the resulting impedance of the capacitor cancels that of the inductor, resulting in a circuit that appears entirely resistive.


text:
# Linked list where user replace a chosen number in the list with a number chosen by user - how can it be improved?

I'm quite new to C programming so I'm trying to learn the basics. I've made a program that creates a linked list of numbers, then ask user for which number he/she wants to replace and then what number should come instead.

I finally got it to work, but since I'm learning this on my own no one is there to say when my style is bad or if I use bad methods for solving my problems. So I kindly ask if you see something that's done in an unwise way to let me know.

So here's the code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node {
int val;
struct node* next;
};

typedef struct node node_t;

// Function that evaluate the value in the nodes of the linked list and replace it.
void replace(node_t ** head, int replacement_value, int new_value) {

while ((*tracer)->next != NULL && (*tracer)->val != replacement_value) {
(*tracer) = (*tracer)->next;
}
(*tracer)->val = new_value;

}

// Function that prints out the linked list.

while (temporary != NULL) {
printf("%d - ", temporary->val);
temporary = temporary->next;
}
printf("\n");
}

// The following creates nodes in the linked list.
node_t *create_new_node(int val) {
node_t *result = malloc(sizeof(node_t));
result->val = val;
result->next = NULL;
return result;
}

int main(){

node_t *tmp;

// The following creates the linked list.
for (int i=0; i<25; i++) {
tmp = create_new_node(i);
}

printf("First print:\n");

int replacement_value;
int new_value;

printf("Which number do you wish to replace?\n");
scanf("%d", &replacement_value);
printf("What number do you want to replace it with?\n");
scanf("%d", &new_value);

printf("Modified print:\n");

return(0);
}

For a new user of C you really aren't doing too bad, you're not using global variables which is very good. The functions are small and well defined. The program as a whole is well organized so that function prototypes are not required.

This program could have a few more function and that would simplify main():

• A function that asks the user for input and performs error checking on the input before returning values, this would also localize the variables for input in the function
• There are some basic linked list operations that are not here that might be helpful insert_node(), delete_node() and append_node() find_node(), other functions such as replace() can utilize these basic functions
• It might be good to have a function that prints a title and then calls printlist() which would reduce the amount of code in main()
• A function to initialize the linked list

## Missing Error Checking

There are two places where error checking in this program, first, it is generally a best practice to error check all user input before using the input values. Users can make mistakes when entering data, they may just hit the enter key without entering data, they may enter a string instead of a number, they may enter a number that is not in the list which could cause problems while searching the list.

The second place where error checking is necessary is after any memory allocation in the C programming language, some or most high level languages will throw exceptions if memory allocation fails. In C programming if memory allocation fails the call to malloc(), calloc() or realloc() returns NULL. It is very important to check the value returned to make sure it is not NULL before using the memory, access through a NULL pointer causes unknown behavior. This can cause a number of problems including the crashing of the program or the corruption of data in the program.

node_t *create_new_node(int val) {
node_t *result = malloc(sizeof(node_t));
if (result == NULL)
{
fprintf(stderr, "malloc failed in create_new_node()\n");
return result;
}
result->val = val;  // Unknown behavior here if malloc() failed
result->next = NULL;
return result;
}

## Include Files That Are Not Necessary

The code contains #include <string.h> however, no functions defined in this include file are utilized. The #include statement copies the contents of the file into the current file, it will increase the compile time and if you are using an editor that also creates a makefile it may add an unnecessary dependency to the makefile. There may also be collisions with functions defined in the code. Basically don't include files you don't need.

## Return From Main

The C compiler is smart enough to add return 0; at the end of this program, if the code does contain multiple returns from main() such as program failure when malloc() fails the code will be more readable if return EXIT_FAILURE; or return EXIT_SUCCESS;. These macros are included from stdlib.h which is already included in this program.

The code would be more readable and easier to maintain if there were spaces between operators and operands for (int i=0; i<25; i++) { versus for (int i = 0; i < 25; i++) {. It would also make the code more readable and maintainable if the 25 in the for loop was a symbolic constant

#define LIST_SIZE 25

...

for (int i = 0; i < LIST_SIZE; i++) {
tmp = create_new_node(i);
if (tmp == NULL)
{
return EXIT_FAILURE;
}
`


text:
# Example: Ligand Field DFT: f-d transitions in Pr 3+¶

Download Pr_LFDFT.run

#!/bin/sh

# Application of the Ligand Field DFT approach for the atomic Pr 4f^2 -> Pr 4f^1
# 5d^1 transition.

# First an average of configuration calculation (AOC) is performed for the 4f^2
# electron configuration, where 2 electrons are equally distributed over the 7
# orbitals that have the most dominant Pr 4f character. Depending on the
# electron configuration this might be a non-trivial task.

SCM_LFDFT="$AMSHOME/examples/adf/Pr_LFDFT/LFDFT" export SCM_LFDFT AMS_JOBNAME=f2$AMSBIN/ams <<eor
System
atoms
Pr        0.000000    0.000000    0.000000
end
end

irrepoccupations
A 54 0.2857143 0.2857143 0.2857143 0.2857143 0.2857143 0.2857143 0.2857143
end
basis
core none
type ZORA/TZ2P+
end
numericalquality good
relativity
level scalar
formalism ZORA
end
symmetry nosym
EndEngine
eor

# Next the an LFDFT calculation is performed including spin-orbit coupling (soc
# 1). In this case there is 1 shell, and the nlval for 4f is '4 3'. The MO
# indices should be the fractionally occupied levels of the AOC calculation (28
# 29 30 31 32 33 34). Results are added on adf.rkf.

$AMSBIN/lfdft <<eor adffile f2.results/adf.rkf nshel 1 nlval 4 3 MOind 28 29 30 31 32 33 34 soc 1 eor rm logfile # Next an average of configuration calculation (AOC) is performed for the 4f^1 # 5d^1 electron configuration, where 1 electron is equally distributed over the # 7 orbitals that have the most dominant Pr 4f character, and 1 electron is # equally distributed over the 7 orbitals that have the most dominant Pr 5d # character. Depending on the electron configuration this might be a non-trivial # task. AMS_JOBNAME=f1d1$AMSBIN/ams <<eor
System
atoms
Pr        0.000000    0.000000    0.000000
end
end

irrepoccupations
A 54 0.1428571 0.1428571 0.1428571 0.1428571 0.1428571 0.1428571 0.1428571 0.2 0.2 0.2 0.2 0.2
end
basis
core none
type ZORA/TZ2P+
end
numericalquality good
relativity
level scalar
formalism ZORA
end
symmetry nosym
EndEngine
eor

# Next the an LFDFT calculation is performed including spin-orbit coupling for
# both 4f and 5d (soc 1 1). In this case there are 2 shells, and the nlval for
# 4f is '4 3', and for 5d '5 2'. The MO indices should be the fractionally
# occupied levels of the AOC calculation for 4f (28 29 30 31 32 33 34), and for
# 5d (35 36 37 38 39). Results are added on adf.rkf.

$AMSBIN/lfdft <<eor adffile f1d1.results/adf.rkf nshel 2 nlval1 4 3 nlval2 5 2 MOind1 28 29 30 31 32 33 34 MOind2 35 36 37 38 39 soc 1 1 eor rm logfile # Next excitation energies are calculated for exciting from the ground state of # the Pr 4f^2 -> Pr 4f^1 5d^1. Input for lfdft_tdm are the 2 .t21 files that were # calculated previously. Results of the excitation energies are added on the # adf.rkf file belonging to state2.$AMSBIN/lfdft_tdm <<eor


text:
# Rotate 2d Array Python

', however I was not able to get it. Also, we have angles, and the respective rotationMatrix. Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem. , 0 1 2 4 5 6 7. To rotate a ring, we need to do following. geeksforgeeks. Default is 0. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. array ( [3, 0, 3, 3, 7, 9]). javascript java c# python android php jquery c++ html ios css sql mysql. Default is 64 bit Float. I have a set of greyscale images as a 2D numpy arrays. Note that the rank of the array is not the rank of the matrix in linear algebra (dimension of the column space) but the number of subscripts it takes! Scalars have rank 0: >>> x = np. Matplotlib's PyLab interface is the set of functions that allows the user to create plots. 05098369] [ 0. Heatmap using 2D numpy array. For this. The Python script to acquire and recolor the images turned out to be pretty compact: from picamera. Hi all, What if you have a 2d array(list, matrix) and you need to rotate it 90, 180, 270 degrees? You can write your own function with a lot of shifts or to use numpy. The goal is to rotate array A K times; that is, each element of A will be shifted to the right by K indexes. Axes method v/s pyplot. This post makes a copy of the original matrix and adds the correct values to it, the second post (coming soon) mutates the original array in-place. The diagonal entries of the covariance matrix are the variances and the other entries are the covariances. OpenCV Python - Rotate Image In this tutorial, we shall learn how to rotate an image to 90, 180 and 270 degrees in OpenCV Python with an example. In our code (see below) we have declared a 2D array called pixels to store the value of each pixel used to represent one of the space. Create a Bitmap object with the given fixed size. An array is one of the data types in java. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. While implementing a Kronecker-product for pedagogical reasons (without using the obvious and readily available np. Could you do it in-place with O (1) extra space? The easiest solution would use additional memory and that is perfectly fine. pygame (the library) is a Free and Open Source python programming language library for making multimedia applications like games. Project details. 1st bite of Python. Logic to right rotate an array. com How to tanspose-2d-array-in-python based on the rows and column using Numpy module declaration syntax of array access the elements and transpose. rotate the list to the right. Utilising from what we have learnt above, the following code below can be used to transform the points [0, 0], [0, 1], [1, 0], [1,1]. As with indexing, the array you get back when you index or slice a numpy array is a view of the original array. Expect the arrays to be randomly generated. Getting started 2nd bite of Python. Think of a perfectly straight line of points parallel to the x axis. s: Size in points^2. Rotate the image by 90 degrees (clockwise). Matplotlib produces high-quality figures like many of the illustrations used in this book. img: PIL Image instance. Rotate the array by given places. Add the elements of a list (or any iterable), to the end of the current list. Simple Animated Plot with Matplotlib by PaulNakroshis Posted on March 23, 2012 Here’s a simple script which is a good starting point for animating a plot using matplotlib’s animation package (which, by their own admission, is really in a beta status as of matplotlib 1. Update: In short, algorithm is this: Finding keypoints of your object image 1. How To Transpose 2D Array In Python - CodeSpeedy. This post makes a copy of the original matrix and adds the correct values to it, the second post (coming soon) mutates the original array in-place. The Python script to acquire and recolor the images turned out to be pretty compact: from picamera. In many languages (Java, COBOL, BASIC) this notion of multi-dimensionality is handled by pre-declaring the dimensions (and limiting the sizes of each dimension). ; Read number of times to rotate in some variable say N. Numpy has an FFT package to do this. Matplotlib's PyLab interface is the set of functions that allows the user to create plots. angle = 65. Leetcode (Python): Combination Sum Given a set of candidate numbers ( C ) and a target number ( T ), find all unique combinations in C where the candidate numbers sums to T. fliplr() specialized for horizontal flipping. Aperiodic, continuous signal, continuous, aperiodic spectrum where and are spatial frequencies in and directions, respectively, and is the 2D spectrum of. The two dimensional rotation matrix which rotates points in the xy plane anti-clockwise through an angle θ about the origin is. To create a heatmap in Python, we can use the seaborn library. I need to rotate the images about one point (inside them) of different, float angles. Python program to left rotate the elements of an array. December 26, 2018 06:51. Rotation of a matrix is represented by the following figure. The process of changing an element of a list is known as "mutating". Some of the operations covered by this tutorial may be useful for other kinds of multidimensional array processing than image processing. Clockwise & Counterclockwise Rotation of a matrix using Numpy Library. import numpy as np import matplotlib. This will make it easier to copy code into and out of the wiki. In the base 8 numbering system where valid numbers are 0, 1, 2, 3, 4, 5, 6 and 7. Solving for the least squares, essentially gives you the correlation coefficient of the points which is related to the axis of rotation of the points from which one gets the angle of rotation. flip — NumPy v1. NumPy offers a lot of array creation routines for different circumstances. This variation on the For Loop Iteration example shows how to use an array. Note that due to our way of solving this, it could be translated easily to objects with more than 4 sides. visiblemap(phi, theta, iangle, rangle) [source] ¶ Return a 2D boolean map that’s True for the planetary latitude, longitude values visible from an observer. Read elements in an array say arr. Due to all operations heavily relying on numpy this is one of the fastest STL editing libraries for Python available. angle = 65. flip() you can flip the NumPy array ndarray vertically (up / down) or horizontally (left / right). 6 for Python 2. Here are a couple of ways to accomplish this in Python. This section will present several examples of using NumPy array manipulation to access data and subarrays, and to split, reshape, and join the arrays. In Place or using extra memory. A modular scientific software toolkit. This lesson teaches you the basics of loading, displaying, and saving images. Imagine a point located at (x,y). Syntactically, NumPy arrays are similar to python lists where we can use subscript operators to insert or change data of the NumPy arrays. It is the same data, just accessed in a different order. Alternately, the transpose method can also be used with one of the constants Image. It has a shape, and you can rotate it using built-in methods instead of reinventing the wheel. This tutorial will introduce you to the translate, rotate, and scale functions so that you can use them in your sketches. METHOD 3 (A Juggling Algorithm) This is an extension of method 2. ; Y (2D array_like object) - An p by m array of p variables and m samples. Rotate the image by 90 degrees (clockwise). Generally you will have a simple generic shape that covers the entity known as a "hitbox" so even though collision may not be pixel perfect, it will look good enough and be performant. rotate(2) >>> d deque([4, 5, 1, 2, 3]) >>> d. When we talk about combining rotation matrices, be sure you do not include the last column of the transform matrix which includes the translation information. Okay, empecemos! Here is Version 1: The full code. NumPy arrays are equipped with a large number of functions and operators that help in quickly writing high-performance code for various types. 3) Move elements of bottom row. Logic to left rotate an array. Today's exercise is simple but tricky: write a function to rotate the elements of an array. Rotate the array by given places. Let us understand what we need to do to solve this particular problem. 2D or 3D, translation: VersorTransform: 3D, rotation represented by a versor: VersorRigid3DTransform: 3D, rigid transformation with rotation represented by a versor: Euler2DTransform: 2D, rigid transformation with rotation represented by a Euler angle: Euler3DTransform: In Python these include Tuple, Numpy array, and List. Using the SavedModel format. Another complimentary package that is based on this data visualization library is Seaborn , which provides a high-level interface to draw statistical graphics. A protip by xiaoba about python, array, and reverse. angle = 65. The rotation vector is a convenient way to represent a $3\times3$ rotation matrix (which has only 3 Degrees Of Freedom) and can be easily converted back to matrix using the cv2. This can be used to place the robot in any desired position and orientation. NumPy arrays are used to store lists of numerical data and to represent vectors, matrices, and even tensors. I highly recommend using 64 bit Python if you can, 32 bit is limited to 2GB of ram, which is quite the limitation. If you wanted to rotate that point around the origin, the coordinates of the new point would be located at (x',y'). Problem with this approach is that it's computationally expensive, especially if I want to start doing more than just one rotation. As with indexing, the array you get back when you index or slice a numpy array is a view of the original array. For instance, given the array [1…. & & Transform 18 points by the rotation matrix. All X2, Y2, Z2 below are 2d arrays of size 49 × 49. 2 (Windows only) Python Imaging Library 1. Rotating a 2D Matrix. Fourier Transform in Numpy¶. The following diagram shows the OpenGL 2D Coordinate System, which corresponds to the everyday 2D Cartesian coordinates with origin located at the bottom-left corner. array([[1, 2, 3. Used in the tutorials. In a straightforward way, we can create a new array and then copy elements to the new array. The image can be loaded using skimage. I need to rotate the images about one point (inside them) of different, float angles. Okay, empecemos! Here is Version 1: The full code. Python has modules that go along with it that allow for image manipulation. The syntax is clear. Handwriting recognition. HyperTools uses dimensionality reduction algorithms to project high-dimensional data onto 2D and 3D plots. To perform 2D transformations such as translation, scaling, and rotation on 2D object. Keep in mind that, unlike Python lists, NumPy arrays have a fixed type. set_style('darkgrid') sns. In these notes, we consider the problem of representing 2D graphics images which may be drawn as a sequence of connected line segments. surf() View a 2D array as a carpet plot, with the z axis representation through elevation the value of the array points. For Rotating a matrix to 90 degrees clockwise, We need to transform each row of a Matrix to a column in rotated matrix. linspace(ymin, ymax, N) Z = np. Using numpy. We use them with enumerators. It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing and motion tracking, video editing and 2D animation pipeline. The trick here is the modulo operation. The rotation vector is a convenient way to represent a $3\times3$ rotation matrix (which has only 3 Degrees Of Freedom) and can be easily converted back to matrix using the cv2. Initialize the graphics mode. For a simple or small coordinate system or grid, nested lists can be useful. One important aspect of presenting data is in Graph format (visual format – also known as Data Visualization). class displayio. This is the most basic way of implementing one step of left rotation on a given array. Circles 4th bite of Python. img_to_array ( img, data_format=None, dtype=None ) Used in the notebooks. It is called the three shear rotation method. python Programming Guide. Thus, 2 types of input are possible. rot90(poles_0,rotate_0). However, the data associated with certain systems (a digital image, a board game, etc. This is an easy mistake to make. array() method. Grid Rotation-Smoothing-Plot Python. (2 replies) Hi, I am looking for some function that would shear my 2D numpy. Matlab's imagesc shows you this quite meaningfully:. Adds an element at the end of the list. A 3d array is a matrix of 2d array. Array Implementation Details. geeksforgeeks. The following diagram shows the OpenGL 2D Coordinate System, which corresponds to the everyday 2D Cartesian coordinates with origin located at the bottom-left corner. When we talk about combining rotation matrices, be sure you do not include the last column of the transform matrix which includes the translation information. Note that ar is array (numpy or scipy) and also note that cnt is an array i. 2) Move elements of last column. 2D Array 3D Algorithm animation array ASCII BBC micro:bit Binary Block Programming Coordinates cryptography CSS CSV encryption Enigma File Handling Flowchart Function Glowscript Graph HTML iteration JavaScript Linear Search List Little Man Computer LMC logic gates Networks Object-Oriented OOP Procedure Pseudocode PyGame Python Python Challenge. Two-dimensional Fourier transform also has four different forms depending on whether the 2D signal is periodic and discrete. METHOD 3 (A Juggling Algorithm) This is an extension of method 2. Rotating an image is definitely the most complicated image processing technique we’ve done thus far. You need to do this in place. The Vectorworks Job Board is dedicated to host online postings for job opportunities at Vectorworks based firms and for Vectorworks users seeking employment to post their resume or qualifications. Sponsored by #native_company# — Learn More. 14159]) # Rotate about z at 0. The problem reduces to traversing the 2-D array in a circular. net c r asp. An image is essentially a standard NumPy array containing pixels of data points. Just like the graphics pipeline, transforming a vector is done step-by-step. In this program, we have an array of elements to count the occurrence of its each element. Python Numpy Library is very useful when working with 2D arrays or multidimensional arrays. Rotate the array by given places. The two dimensional rotation matrix which rotates points in the xy plane anti-clockwise through an angle θ about the origin is. Project details. Think of a perfectly straight line of points parallel to the x axis. Rotation of the above array by 2 will make array. So python is assuming you want to convert an octal number to a decimal number. Then print the updated array as a single line of space-separated integers. A protip by xiaoba about python, array, and reverse. Graph Slam Python. NumPy: Rotate array (np. Array consists of data of any data type. Reversal Algorithm for ROTATION of an array. fromarray(arr) img. In this program, we need to rotate the elements of an array towards the left by the specified number of times. A string in Python is a sequence of characters. The seaborn library is built on top of Matplotlib. It has a shape, and you can rotate it using built-in methods instead of reinventing the wheel. Developer Support. The job of transforming 3D points into 2D coordinates on your screen is also accomplished through matrix transformations. This section will present several examples of using NumPy array manipulation to access data and subarrays, and to split, reshape, and join the arrays. Rotating a two-dimensional array in Python I was solving one of the learning tasks on Python and had to rotate two dimensional array clockwise. In plain Python, we can represent such a matrix as a list of lists:. In Python, this is the main difference between arrays and lists. Update: In short, algorithm is this: Finding keypoints of your object image 1. py --image images/saratoga. Vectorize Image with Python scikit-image With imread we get a 3D numpy array. Below is the step by step descriptive logic to rotate an array to right by N positions. the number of features like height, width, weight, …). Used in the guide. Thanks Radek. It's like a series of linked cups, all of which can hold the same maximum value. It's often referred to as np. I also showed how to visualize them with static 3-D plots. sin(theta)],. Within the C code (backend for python functions), arrays are stored in 1D, C-order and are usually named p_map_v in the code. Also, as you can imagine, N can be large as well. It so happens that OpenGL has a function called "point sprites", which basically allows you to draw the contents of a texture on a square centered around the vertices, which makes it very easy to copy gnuplot's with points drawing style. a matrix is a two dimensional array. Rotate the image by 90 degrees (clockwise). The above solution to How to Rotate a 2D Matrix by 90 Degrees in Java simply uses the same formula (i. Okay, empecemos! Here is Version 1: The full code. At the core of NumPy is a class called ndarray for modeling homogeneous n-dimensional arrays and matrices. Python has a set of built-in methods that you can use on lists/arrays. array_1 * 5 np. org Mailing Lists: Welcome! Below is a listing of all the public Mailman 2 mailing lists on mail. A protip by xiaoba about python, array, and reverse. For those that are unfamiliar with what Smolyak interpolation is, it is a sparse grid collocation method that uses perpendicular polynomials for accurate interpolation between grid points. Matrix Class:. \$\begingroup\$ @CleverProgramer Oh sorry, I said that if the size of the array is 5, and the shift amount is 11, the array will be the same if shifted 11 times as if shifted 1 time (multiples of 5, or whatever the size of the array is, will leave you with the same exact array). Exhaustive, simple, beautiful and concise. kron()), I obtained a 4 dimensional array as an intermediate result, which I've to reshape to get the final result. Also the covariance matrix is symmetric since σ(xi,xj)=σ(xj,xi) σ ( x i, x j) = σ ( x j, x i). 2) Move elements of last column. To create a NumPy array we need to pass list of element values inside a square bracket as an argument to the np. = array(' ', ) # Treats array as a sequence of numbers. coordinate-systems rotations python. Code: Select all uv_poles_0 = np. Either an array of the same length as xs and ys or a single value to place all points in the same plane. returns (phi2,theta2) phi2 will be in the range (0,2pi) and theta2 will be in the range (-pi/2,pi/2) maps. com How to tanspose-2d-array-in-python based on the rows and column using Numpy module declaration syntax of array access the elements and transpose. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. You are given a 2D matrix of dimension and a positive integer. The default OpenGL 2D clipping-area (i. Required knowledge. Such images may be represented as a matrix of 2D points. To perform 2D transformations such as translation, scaling, and rotation on 2D object. There are also other good books like – ‘Python for Data Analysis’, ‘ Python: Data Analytics and Visualization ‘ , ‘Python for Finance’ etc. improve this question. This section addresses basic image manipulation and processing using the core scientific modules NumPy and SciPy. Algorithms to detect collision in 2D games depend on the type of shapes that can collide (e. NumPy arrays are equipped with a large number of functions and operators that help in quickly writing high-performance code for various types. With this behavior it is possible to open also DXF drawings that contains data from 3rd party applications. A cleaner way to do this is make a helper method. Use the affine Python library instead. Write a function rotate(ar[], d, n) that rotates arr[] of size n by d elements. NET Java Jobs. geeksforgeeks. table("data. Lets create a 2D array call M to store the minimum energy value seen upto that pixel. 2D Plotter The idea of this project was to create an ultrasonic radar by mounting an ultrasonic sensor on a stepper motor. Raster data coordinate handling with 6-element geotransforms is a pain. 16 Manual numpy. Note that due to our way of solving this, it could be translated easily to objects with more than 4 sides, or more than 2 dimensions. Let us understand what we need to do to solve this particular problem. 2D Array 3D Algorithm animation array ASCII BBC micro:bit Binary Block Programming Coordinates cryptography CSS CSV encryption Enigma File Handling Flowchart Function Glowscript Graph HTML iteration JavaScript Linear Search List Little Man Computer LMC logic gates Networks Object-Oriented OOP Procedure Pseudocode PyGame Python Python Challenge. odei Try using all mathtext fontset in python and matpl Generate average image using Python and PIL (Pytho Combine 3D and two 2D animations in one figure usi Combine 3D and two 2D animations in one figure usi. NumPy provides the reshape() function on the NumPy array object that can be used to reshape the data. In the 3rd dimension are the RGB values: 2. filter_pcorr (int) – Radius of a spectrum filter for translation detection. Rotate the image by 90 degrees (clockwise). Guide to using and configuring the Unreal Editor toolset. ndarray contains elements of the same data type. #!/usr/bin/python -tt import sys #create a N X N matrix def getMatrix(n): matrix = [] for i in range(n): inside = [] for j in range(n): inside. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. The image can be loaded using skimage. , a 2x2 square with centered at. A (moving) light source position is transferred from python to GLSL via the GL_LIGHT0 variables. I have a straight-forward algorithm which can output the desired result in-place (Not requiring any additional space, apart from the 2-D array). I highly recommend using 64 bit Python if you can, 32 bit is limited to 2GB of ram, which is quite the limitation. zdir: Which direction to use as z ('x', 'y' or 'z') when plotting a 2D set. Handwriting recognition. For a square array, we can do this inplace. A cleaner way to do this is make a helper method. Today's exercise is simple but tricky: write a function to rotate the elements of an array. 2 Accessing Objects. The problem reduces to traversing the 2-D array in a circular. glMatrixMode (GL_PROJECTION) # the matrix that transforms 3d into a 2d perspective picture glLoadIdentity ( ) # resets the matrix to a default state - anythign multiplied by this returns itself, like 1. It is a derived data type. 2) Move elements of last column. We are providing an easy example for a better understanding. Project description. we will talk about step by step in later with practical. More loops 6th bite of Python. Develop a way to rotate the data as if you rotated the data by 90 degrees. The following article 2D Arrays in Java provides an outline for the creation of 2D arrays in java. Right rotate the given array by 1 for N times. Keywords: Modeling, J Programming Language, 2D Graphics Transformations. Shaan - see rotation matrix which you can construct to rotate your (x,y) points (of your 2D shape) so that you can rotate them counter-clockwise. Leetcode (Python): Add Two Numbers You are given two linked lists representing two non-negative numbers. 6 for Python 2. 3D Programming In Python. Reshape 1D to 2D Array. We'll be using only python and its official GUI, tkinter (so no official 3D engine will be used like OpenGL(PyOpenGL, PyGame) or Direct3D). Last Updated: December 26, 2018 · 27. flipud() specialized for vertical flipping and numpy. 05K · xiaoba. Method 4 (The Reversal Algorithm) : Algorithm : Python # Python program for. The function takes two arguments: the array to be rotated and the number of elements to rotate, where a positive count rotates to the left and a negative count rotates to the right. The above solution to How to Rotate a 2D Matrix by 90 Degrees in Java simply uses the same formula (i. im0 (2D numpy array) – The first (template) image; im1 (2D numpy array) – The second (subject) image; numiter (int) – How many times to iterate when determining scale and rotation; order (int) – Order of approximation (when doing transformations). To create and apply a rotation matrix using python, a solution is to use numpy: \left( \begin{array}{cc} Rotation of a 2D array over an angle using rotation matrix: stackoverflow: Faster way to generate a rotation matrix? scipy: Matrice de rotation: wikipedia: Add a comment :. In case you want to create 2D numpy array or a matrix, simply pass python list of list to np. Required knowledge. describes the dimension or number of random variables of the data (e. One by one rotate all rings of elements, starting from the outermost. In the below example of a two dimensional array, observer that each array element itself is also an array. I have a set of greyscale images as a 2D numpy arrays. Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem. Rodrigues(R)[0] #I only use the first return value. In a straightforward way, we can create a new array and then copy elements to the new array. roll(bits, 45) # rotate 45 degrees Unfortunately, this just does a circular shift, not an actual angular rotation. Python program to find the frequency of each element in the array. Subject Areas: 2D Graphics Transformations. Template matching with matchTemplate is not good when your object is rotated or scaled in scene. requires a 2-D array Z that speci es function values on a grid. 2d array rotation: so i have to write a program tht does all this: void rotateRowRight(char A[][SIZE], int row, int size) which performs a right rotate on the first size elements of row row. open("input. Guide to using and configuring the Unreal Editor toolset. Given an array of integers and a number, , perform left rotations on the array. 2 Accessing Objects. You are given a 2D matrix of dimension and a positive integer. array 2D ndarray of double. Python Program for array rotation Write a function rotate(ar[], d, n) that rotates arr[] of size n by d elements. Rotate X,Y (2D) coordinates around a point or origin in Python - rotate_2d_point. Rotation of a matrix is represented by the following figure. For example a 3x3 matrix which describes a rotation of a vector in three dimensional space an be represented as an array of rank two. The rotate () method of Python Image Processing Library Pillow takes number of degrees as a parameter and rotates the image in counter clockwise direction to the number of degrees specified. Array is a group of homogeneous data items which has a common name. Improve this sample solution and post your code through Disqus. print x [1:4] # second to fourth element. We will be rotating the matrix 90 degrees. empty((N, N)) for i, y in enumerate(Y): for j, x in. As with one dimensional arrays, every cell in a 2D array is of the same type. Here is an example of an CosDict Object Instance ann1, ">". For example, the rotation of array A = [3, 8, 9, 7, 6] is [6, 3, 8, 9, 7]. array(10) >>> x array(10) >>> np. The element at ith row and jth column in X will be placed at jth row and ith column in X'. You have to rotate the matrix times and print the resultant matrix. Well, thanks for the A2A Siva Chaitanya. At a rotation of 90°, all the cos components will turn to zero, leaving us with (x',y') = (0, x. In matrix notation, this can be written as: As a sanity check, consider a point on the x-axis. Example 1: Given input matrix = [ [1,2,3], [4,5,6], [7,8,9] ], rotate the input matrix in-place such that it becomes: [ [7,4,1], [8,5. Link [Algo] Matrix Rotation Complexity: time complexity is O(N×M) space complexity is O(NxM) Execution: There is just lots of code, but the actual solution is pretty simple. I need to rotate the images about one point (inside them) of different, float angles. Python Program for array rotation. rangle and iangle are the rotation and inclination angles of the planet in radians. geeksforgeeks. Hi there! LÖVE is an *awesome* framework you can use to make 2D games in Lua. Creating a numpy array using np. transform) can be used to scale, translate, rotate, and shear the original image. A left rotation operation on an array of size shifts each of the array's elements unit to the left. Start from examples or try it in your browser! 2019-02-02 Full Totem Analysis based on. min(ar,axis=0) maxa = np. The seaborn library is built on top of Matplotlib. This will involve reading metadata from the DICOM files and the pixel-data itself. surf() View a 2D array as a carpet plot, with the z axis representation through elevation the value of the array points. Blender is the free and open source 3D creation suite. Find Complete Code at GeeksforGeeks Article: http://www. Each band can be viewed as a separate 2D data array but every band in the same file will have the same array dimension (or shape, in Numpy lingo). In programming we can use a 2D array data structure to represent a graphic. Circles 4th bite of Python. So, if you are using 32 bit Python, you need to use 32 bit modules, and so on. Rotate image. You are given an n x n 2D matrix representing an image. The typical geospatial coordinate reference system is defined on a cartesian plane with the 0,0 origin in the bottom left and X and Y increasing as you go up and to the right. A Python package to create and modify DXF drawings, independent from the DXF version. visiblemap(phi, theta, iangle, rangle) [source] ¶ Return a 2D boolean map that’s True for the planetary latitude, longitude values visible from an observer. This index i can be determined by the number N which represents the number of rotations we want to perform on the given array and then return the result. Pour créer et appliquer une matrice de rotation avec python on peut tout simplement utiliser numpy: \left( \begin{array}{cc} \cos(\theta) & -\sin(\theta) \\. I suggest that you use a library which provides you with proper multidimensional arrays. These 1d arrays will be used later to draw some plots as well. If you wanted to rotate that point around the origin, the coordinates of the new point would be located at (x',y'). You need to do this in place. EhouarnPerret. \$ python rotate_simple. I have a set of greyscale images as a 2D numpy arrays. It provides all the functionalities needed to deal with big data processing, statistical analysis, visualisation and storage. Rotation of the array means that each element is shifted right by one index, and the last element of the array is also moved to the first place. So if the rotation value of the glyph is 3 (270 degrees) then we select the last cube in the array, which is cube_3. The above solution to How to Rotate a 2D Matrix by 90 Degrees in Java simply uses the same formula (i. Python Numpy Library is very useful when working with 2D arrays or multidimensional arrays. Python program to left rotate the elements of an array. Rotating a MxN array is trivial if you have extra O(NM) memory. Even further dimensions can be added. array import PiRGBArray from picamera import PiCamera from sys import argv # get this with: pip install color_transfer from color_transfer import color_transfer import time import cv2 # init the camera camera = PiCamera() rawCapture = PiRGBArray(camera) # camera to warmup time. Save in new array. Opencv is. Over the course of this series of articles we've seen how to decompose. flip — NumPy v1. NumPy: Rotate array (np. Python program to left rotate the elements of an array. Note that numpy. data: Pass value as a 2D or rectangular numpy array or pandas DataFrame; To create a heatmap using python sns library, data is the required parameter. You can open/save every DXF file without losing any content (except comments), Unknown tags in the DXF file will be ignored but preserved for saving. Utilising from what we have learnt above, the following code below can be used to transform the points [0, 0], [0, 1], [1, 0], [1,1]. Blender is the free and open source 3D creation suite. This gives you a "sublist" of the original list described by [start:end:step], start is the first element, end is the last element to be used in the sublist. Pretty nets 7th bite of Python. NumPy arrays are used to store lists of numerical data and to represent vectors, matrices, and even tensors. Subject Areas: 2D Graphics Transformations. Note: Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem. In the introduction I explained the idea: Using Python to program old skool demo style real-time vector graphics. NumPy is a Python library that can be used for scientific and numerical applications and is the tool to use for linear algebra operations. Python has modules that go along with it that allow for image manipulation. To read an image in Python using OpenCV, use cv2. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. waitKey(0) Take a look at Grant. ; Left Rotate the given array by 1 for N times. Link [Algo] Matrix Rotation Complexity: time complexity is O(N×M) space complexity is O(NxM) Execution: There is just lots of code, but the actual solution is pretty simple. Once installed, in python you may create the orientation object which can rotate vectors, or be part of transform objects. Pour créer et appliquer une matrice de rotation avec python on peut tout simplement utiliser numpy: Rotation of a 2D array over an angle using rotation matrix: Comment créer et appliquer une matrice de rotation avec python ? Previous Next. I think, you need to look at the rotate helper function from SciPy package. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. position relative to the center of rotation: Let's add new indexes that define the offset with respect to the center of rotation; for the cell (i,j), this offset is (i-ic, j-jc). Rotation of the above array by 2 will make array. In programming we can use a 2D array data structure to represent a graphic. A NumPy array is an extension of a usual Python array. Okay, empecemos! Here is Version 1: The full code. The array must be stored as-is without any changes made to it until after this first line. , a 2x2 square with centered at. For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4]. Build Array adds rows to a 2D array (read the Help). Could you do it in-place with O (1) extra space? The easiest solution would use additional memory and that is perfectly fine. In this program, we need to rotate the elements of an array towards the left by the specified number of times. 2-dimensional array structured as a matrix. An array is a data structure that stores values of same data type. = array(' ', ) # Treats array as a sequence of numbers. This is why displaying the image directly displays only a line, it is seen as just a column of. R =(cosθ −sinθ sinθ cosθ). Note that the rank of the array is not the rank of the matrix in linear algebra (dimension of the column space) but the number of subscripts it takes! Scalars have rank 0: >>> x = np. python使用tkinter开发一款五子棋游戏. NumPy is a Python library that can be used for scientific and numerical applications and is the tool to use for linear algebra operations. Rotate Array Rotate Array. Below is the step by step descriptive logic to rotate an array to right by N positions. You can see these new matrices as sub-transformations of the space. geeksforgeeks. You should try openCV function from Features2D Framework. Extract elements by specifying an array of indices: The take() method of numpy. surf() View a 2D array as a carpet plot, with the z axis representation through elevation the value of the array points. 05098369] [ 0. An array is one of the data types in java. img: PIL Image instance. im0 (2D numpy array) – The first (template) image; im1 (2D numpy array) – The second (subject) image; numiter (int) – How many times to iterate when determining scale and rotation; order (int) – Order of approximation (when doing transformations). reshape(image_2d, (row_count,column_count,plane_count)) NumPy array to PNG - For writing that you asked in that question above. Given an array, rotate the array to the right by k steps, where k is non-negative. Rotating a 2D Array by 90 Degrees (Python) 1 question Rotating a 2D Array by 90 Degrees (Java) 1 question Rotating 2D Array (Out-of-Place Solution) 05:20 Then, I'm going to walk you through the 11 essential coding interview questions and their answers. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. We are providing an easy example for a better understanding. table("data. Here is a good example of finding rotated object in scene. It does not support multidimensional arrays. We summarize this full decomposition below. This allows us to use mathematical-like notation. One by one rotate all rings of elements, starting from the outermost. exp(array_1) np. You should try openCV function from Features2D Framework. Template matching with matchTemplate is not good when your object is rotated or scaled in scene. Bitmap – Stores values in a 2D array¶ Stores values of a certain size in a 2D array. Rotate Array Rotate Array. First Iteration. Improve this sample solution and post your code through Disqus. 1st bite of Python. Featuring an extensive Python API, every tool is available for scripting and customization. Method 1: For rotating the array. Develop a way to rotate the data as if you rotated the data by 90 degrees. Write a function:. Circles 4th bite of Python. surf() View a 2D array as a carpet plot, with the z axis representation through elevation the value of the array points. I need to rotate a point with UpVector. LeetCode - Rotate Image (Java) You are given an n x n 2D matrix representing an image. In a straightforward way, we can create a new array and then copy elements to the new array. Liste 2D Python × Après avoir cliqué sur "Répondre" vous serez invité à vous connecter pour que votre message soit publié. If you wanted to rotate that point around the origin, the coordinates of the new point would be located at (x',y'). Objective : We will be given one 2D array we need to rotate the array by 90 degree or by given degree. The blue dots in figure 3. I have a straight-forward algorithm which can output the desired result in-place (Not requiring any additional space, apart from the 2-D array). It's often referred to as np. Dec 29, 2016. The seaborn library is built on top of Matplotlib. You can do rotation in following way >>> from collections import deque >>> d deque([1, 2, 3, 4, 5]) >>> d. reshape(-1, 1) if your data has a single feature or array. Another complimentary package that is based on this data visualization library is Seaborn , which provides a high-level interface to draw statistical graphics. Description. max(ar,axis=0) diff. the full camera matrix into intrinsic and extrinsic matrices, the extrinsic matrix into 3D rotation followed by translation, and; the intrinsic matrix into three basic 2D transformations. Rate this: Please Sign up or sign in to vote. rot90(poles_0,rotate_0). rotatedNodes: nodes as rotated to the current angles. One important aspect of presenting data is in Graph format (visual format – also known as Data Visualization). The typical geospatial coordinate reference system is defined on a cartesian plane with the 0,0 origin in the bottom left and X and Y increasing as you go up and to the right. Numpy has an FFT package to do this. It's so clever that it's worth sharing in full detail. Note that ar is array (numpy or scipy) and also note that cnt is an array i. a[5] = {10, 20, 30, 20, 40} and search Item = 20. deque (usually pronounced like "deck") is an irregular acronym of d ouble- e nded que ue. You are given an n x n 2D matrix representing an image. angle = 65. flipud — NumPy v1. dtype: data type of the elements. LeetCode-Python; Introduction 074 Search a 2D Matrix 075 Sort Colors 076 Minimum Window Substring 077 Combinations 078 Subsets 079 Word Search 080 Remove Duplicates from Sorted Array II LeetCode解题之Rotate Array. Python supports only single dimensional arrays. A) Translation. Some of the operations covered by this tutorial may be useful for other kinds of multidimensional array processing than image processing. python Programming Guide. Could you do it in-place with O (1) extra space? The easiest solution would use additional memory and that is perfectly fine. To perform the rotation on a plane point with standard. Rotate Array Rotate Array. asked Dec 7 '11 at 19:31. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation. scale, translate, rotate, and shear the original image. The ZIM framework provides conveniences, components, and controls for coding creativity on the canvas — includes accessibility and hundreds of colorful tutorials. When working with mathematics and plotting graphs or drawing points, lines, and curves on images, Matplotlib is a good graphics library with much more powerful features than the plotting available in PIL. In python seaborn tutorial, we are going to learn about seaborn heatmap or sns heatmap. Link [Algo] Matrix Rotation Complexity: time complexity is O(N×M) space complexity is O(NxM) Execution: There is just lots of code, but the actual solution is pretty simple. Circles 4th bite of Python. What is a matrix? Matrix is a two-dimensional array. Translation: Moving the Grid. #Description: Given a NxN size 2D array of numbers. Jill> How do I define a 2d list? Python doesn't truly have 2d lists in the way you might think of 2d arrays in C or Fortran. The first line of the program can store the array as a variable for 0 points. Returns: A unit quaternion describing the rotation rate q_dot = my_quaternion. I generated a cartesian grid in Python using NumPy's linspace and meshgrid, and I obtained some data over this 2D grid from an unknown function. An integer array is more compact in memory than an integer list. These 1d arrays will be used later to draw some plots as well. warpAffine and cv2. R =(cosθ −sinθ sinθ cosθ). flip — NumPy v1. rotate(2) >>> d deque([4, 5, 1, 2, 3]) >>> d. step says take every step'th element from first to last. It has 1d lists which can contain any Python object, including other lists. For this. data: Pass value as a 2D or rectangular numpy array or pandas DataFrame; To create a heatmap using python sns library, data is the required parameter. This means, for example, that if you attempt to insert a floating-point value to an integer array, the value will be silently truncated. Saving the contents of a Java 2D image to an external GIF, PNG, or JPEG image file. position relative to the center of rotation: Let's add new indexes that define the offset with respect to the center of rotation; for the cell (i,j), this offset is (i-ic, j-jc). How many different ways do you know to solve this problem? Solution 1 - Intermediate Array. Sort Implementation Details. c: A color. As an example, consider the matrix A = (21 −11) that transforms an arbitrary vector (xy) to a linear combination of the column vectors of A : (uv) =. The rotation doesn’t need to be in place, and I will allow (of course, if I explained well so far) for interpolation.
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