Calculating a correlation on Android

correlation.java

/*
 * We've collected a week's worth of data about ice cream consumption
 * and general happiness for a particular individual
 */

double[] iceCreamPerDay = new double[] {
        1, // Day one, had 1 ice cream
        0, // Day two, no ice cream :(
        0, // Etc
        1,
        2,
        1,
        0 };

// Happiness is rated on a 1 to 10 scale
double[] happinessPerDay = new double[] { 7, 5, 4, 6, 9, 9, 5 };

PearsonsCorrelation math = new PearsonsCorrelation();
double correlation = math.correlation(iceCreamPerDays, happinessPerDays);
// outputs: 0.8713708444711573