StdDevFunction.java

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package edu.rice.cs.hpc.data.experiment.metric;

import com.graphbuilder.math.func.Function;

public class StdDevFunction implements Function {

    public StdDevFunction() {}

    public double of(double[] d, int numParam) {
        double sum = 0, sqrsum = 0;
        double mean, stdev;

        for (int i = 0; i < numParam; i++) {
            sum += d[i];
            sqrsum += (d[i] * d[i]);
        }

        mean = sum / numParam;
        stdev = (sqrsum) / numParam - (mean * mean);
        return java.lang.Math.sqrt(stdev);
    }

    public boolean acceptNumParam(int numParam) {
        return numParam > 0;
    }

    public String toString() {
        return "stdev(x1, x2, ..., xn)";
    }
    
    static public void main(String args[]) {
        double num[] = {1,2,4,5};
        final double answer = 1.83;
        StdDevFunction f = new StdDevFunction();
        double result = f.of(num, num.length);
        System.out.println("Result = "+result+" correct answer = "+answer+" test: " + (result == answer));
    }
}