content: /*
   *    This program is free software; you can redistribute it and/or modify
   *    it under the terms of the GNU General Public License as published by
   *    the Free Software Foundation; either version 2 of the License, or
   *    (at your option) any later version.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    GNU General Public License for more details.
   *
   *    You should have received a copy of the GNU General Public License
   *    along with this program; if not, write to the Free Software
   *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  /*
   *    Stats.java
   *    Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
   *
   */
  
  package weka.experiment;
  
  import weka.core.RevisionHandler;
  import weka.core.RevisionUtils;
  import weka.core.Utils;
  
  import java.io.Serializable;
  
  /**
   * A class to store simple statistics
   *
   * @author Len Trigg (trigg@cs.waikato.ac.nz)
   * @version $Revision: 1.12 $
   */
  public class Stats
    implements Serializable, RevisionHandler {
  
    /** for serialization */
    private static final long serialVersionUID = -8610544539090024102L;
    
    /** The number of values seen */
    public double count = 0;
  
    /** The sum of values seen */
    public double sum = 0;
  
    /** The sum of values squared seen */
    public double sumSq = 0;
  
    /** The std deviation of values at the last calculateDerived() call */    
    public double stdDev = Double.NaN;
  
    /** The mean of values at the last calculateDerived() call */    
    public double mean = Double.NaN;
  
    /** The minimum value seen, or Double.NaN if no values seen */
    public double min = Double.NaN;
  
    /** The maximum value seen, or Double.NaN if no values seen */
    public double max = Double.NaN;
      
    /**
     * Adds a value to the observed values
     *
     * @param value the observed value
     */
    public void add(double value) {
  
      add(value, 1);
    }
  
    /**
     * Adds a value that has been seen n times to the observed values
     *
     * @param value the observed value
     * @param n the number of times to add value
     */
    public void add(double value, double n) {
  
      sum += value * n;
      sumSq += value * value * n;
      count += n;
      if (Double.isNaN(min)) {
        min = max = value;
      } else if (value < min) {
        min = value;
      } else if (value > max) {
        max = value;
      }
    }
  
    /**
     * Removes a value to the observed values (no checking is done
     * that the value being removed was actually added). 
     *
     * @param value the observed value
     */
    public void subtract(double value) {
      subtract(value, 1);
    }
  
    /**
     * Subtracts a value that has been seen n times from the observed values
     *
     * @param value the observed value
     * @param n the number of times to subtract value
     */
    public void subtract(double value, double n) {
      sum -= value * n;
      sumSq -= value * value * n;
      count -= n;
    }
  
    /**
     * Tells the object to calculate any statistics that don't have their
     * values automatically updated during add. Currently updates the mean
     * and standard deviation.
     */
    public void calculateDerived() {
  
      mean = Double.NaN;
      stdDev = Double.NaN;
      if (count > 0) {
        mean = sum / count;
        stdDev = Double.POSITIVE_INFINITY;
        if (count > 1) {
  	stdDev = sumSq - (sum * sum) / count;
  	stdDev /= (count - 1);
          if (stdDev < 0) {
  	  //          System.err.println("Warning: stdDev value = " + stdDev 
  	  //                             + " -- rounded to zero.");
            stdDev = 0;
          }
  	stdDev = Math.sqrt(stdDev);
        }
      }
    }
      
    /**
     * Returns a string summarising the stats so far.
     *
     * @return the summary string
     */
    public String toString() {
  
      calculateDerived();
      return
        "Count   " + Utils.doubleToString(count, 8) + '\n'
        + "Min     " + Utils.doubleToString(min, 8) + '\n'
        + "Max     " + Utils.doubleToString(max, 8) + '\n'
        + "Sum     " + Utils.doubleToString(sum, 8) + '\n'
        + "SumSq   " + Utils.doubleToString(sumSq, 8) + '\n'
        + "Mean    " + Utils.doubleToString(mean, 8) + '\n'
        + "StdDev  " + Utils.doubleToString(stdDev, 8) + '\n';
    }
    
    /**
     * Returns the revision string.
     * 
     * @return		the revision
     */
    public String getRevision() {
      return RevisionUtils.extract("$Revision: 1.12 $");
    }
  
    /**
     * Tests the paired stats object from the command line.
     * reads line from stdin, expecting two values per line.
     *
     * @param args ignored.
     */
    public static void main(String [] args) {
  
      try {
        Stats ps = new Stats();
        java.io.LineNumberReader r = new java.io.LineNumberReader(
  				   new java.io.InputStreamReader(System.in));
        String line;
        while ((line = r.readLine()) != null) {
          line = line.trim();
          if (line.equals("") || line.startsWith("@") || line.startsWith("%")) {
            continue;
          }
  	java.util.StringTokenizer s 
            = new java.util.StringTokenizer(line, " ,\t\n\r\f");
  	int count = 0;
  	double v1 = 0;
  	while (s.hasMoreTokens()) {
  	  double val = (new Double(s.nextToken())).doubleValue();
  	  if (count == 0) {
  	    v1 = val;
  	  } else {
              System.err.println("MSG: Too many values in line \"" 
                                 + line + "\", skipped.");
  	    break;
  	  }
  	  count++;
  	}
          if (count == 1) {
            ps.add(v1);
          }
        }
        ps.calculateDerived();
        System.err.println(ps);
      } catch (Exception ex) {
        ex.printStackTrace();
        System.err.println(ex.getMessage());
      }
    }
  
  } // Stats
  
  