source: anac2020/BlingBling/src/main/java/geniusweb/blingbling/Distribution.java

package geniusweb.blingbling;

import java.util.Map;
import java.util.LinkedHashMap;

//record the distribution. Not used yet.
public class Distribution {
    private double mu = 0.0;
    private double var = 0.0;
    private int n = 0;

    private Double min = null;
    private Double max = null;

    public void addSample(double sample) {
        double mu_new = ((double) n * mu + sample) / ((double) n + 1.0);

        var = ((double) n * var + (double) n * Math.pow(mu - mu_new, 2.0) + Math.pow(sample - mu_new, 2.0)) / ((double) n + 1.0);
        mu = mu_new;

        n++;

        if ((min == null) || (sample < min))
            min = sample;
        if ((max == null) || (sample > max))
            max = sample;
    }

    public double getStdDev() {
        return Math.sqrt(var);
    }

    public double getMean() {
        return mu;
    }

    public Map<String, String> toMap(String name) {
        Map<String, String> map = new LinkedHashMap<String, String>();

        map.put(name + "_mean", String.valueOf(mu));
        map.put(name + "_stdDev", String.valueOf(Math.sqrt(var)));
        map.put(name + "_min", String.valueOf(min));
        map.put(name + "_max", String.valueOf(max));

        return map;
    }
}