content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.bigtop.datagenerators.weatherman.internal;
  
  import org.apache.bigtop.datagenerators.samplers.SeedFactory;
  import org.apache.bigtop.datagenerators.samplers.samplers.ConditionalSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.GammaSampler;
  import org.apache.bigtop.datagenerators.samplers.samplers.Sampler;
  
  public class WindSpeedSampler implements
          ConditionalSampler<WeatherRecordBuilder, WeatherRecordBuilder> {
    private final double coeffReal;
    private final double coeffImag;
    private final Sampler<Double> gamma;
  
    public WindSpeedSampler(double windSpeedRealCoeff, double windSpeedImagCoeff,
            double windSpeedK, double windSpeedTheta, SeedFactory seedFactory) {
      coeffReal = windSpeedRealCoeff;
      coeffImag = windSpeedImagCoeff;
  
      gamma = new GammaSampler(windSpeedK, windSpeedTheta, seedFactory);
  
    }
  
    /**
     *
     * @param temp
     *          - given in Fahrenheit
     * @param windSpeed
     *          - given in MPH
     * @return
     */
    private Double windChill(double temp, double windSpeed) {
      double v_16 = Math.pow(windSpeed, 0.16);
      double windChill = 35.74 + 0.6215 * temp - 35.74 * v_16
              + 0.4275 * temp * v_16;
  
      return windChill;
    }
  
    public WeatherRecordBuilder sample(WeatherRecordBuilder weatherRecord)
            throws Exception {
  
      double dayOfYear = weatherRecord.getDate().getDayOfYear();
      // meters/second
      double windSpeed = Math.max(0.0,
              coeffReal
                      * Math.cos(-2.0 * Math.PI * dayOfYear
                              / WeatherConstants.TEMPERATURE_PERIOD)
              + coeffImag * Math.sin(-2.0 * Math.PI * dayOfYear
                      / WeatherConstants.TEMPERATURE_PERIOD) + gamma.sample());
  
      double windChill = windChill(weatherRecord.getTemperature(),
              windSpeed * WeatherConstants.M_PER_S_TO_MPH);
  
      weatherRecord.setWindSpeed(windSpeed);
      weatherRecord.setWindChill(windChill);
  
      return weatherRecord;
    }
  }
  