source: src/main/java/agents/ai2014/group11/Statistics.java@ 126

package agents.ai2014.group11;

import java.util.Arrays;

/**
 * Class to use for basic statistics.
 * 
 * Source:
 * http://stackoverflow.com/questions/7988486/how-do-you-calculate-the-variance-median-and-standard-deviation-in-c-or-java
 */
public class Statistics {

        /**
         * Get the mean of dataset
         * @param data
         * @return
         */
        public static double getMean(double[] data) {
                double sum = 0.0;
                for (double a : data)
                        sum += a;
                return sum / data.length;
        }

        /**
         * Get the variance of dataset
         * @param data
         * @return
         */
        public static double getVariance(double[] data) {
                double mean = getMean(data);
                double temp = 0;
                for (double a : data)
                        temp += (mean - a) * (mean - a);
                return temp / data.length;
        }

        /**
         * Get the standard deviation of dataset
         * @param data
         * @return
         */
        public static double getStdDev(double[] data) {
                return Math.sqrt(getVariance(data));
        }

        /**
         * Get the median of dataset
         * @param data
         * @return
         */
        public static double median(double[] data) {
                double[] b = new double[data.length];
                System.arraycopy(data, 0, b, 0, b.length);
                Arrays.sort(b);

                if (data.length % 2 == 0) {
                        return (b[(b.length / 2) - 1] + b[b.length / 2]) / 2.0;
                } else {
                        return b[b.length / 2];
                }
        }
}