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Calculate The Pearson's Correlation In JAVA

12.21.2007
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        // calculate the Pearson's correlation in JAVA

public class Correlation {
    public static double getPearsonCorrelation(double[] scores1,double[] scores2){
        double result = 0;
        double sum_sq_x = 0;
        double sum_sq_y = 0;
        double sum_coproduct = 0;
        double mean_x = scores1[0];
        double mean_y = scores2[0];
        for(int i=2;i<scores1.length+1;i+=1){
            double sweep =Double.valueOf(i-1)/i;
            double delta_x = scores1[i-1]-mean_x;
            double delta_y = scores2[i-1]-mean_y;
            sum_sq_x += delta_x * delta_x * sweep;
            sum_sq_y += delta_y * delta_y * sweep;
            sum_coproduct += delta_x * delta_y * sweep;
            mean_x += delta_x / i;
            mean_y += delta_y / i;
        }
        double pop_sd_x = (double) Math.sqrt(sum_sq_x/scores1.length);
        double pop_sd_y = (double) Math.sqrt(sum_sq_y/scores1.length);
        double cov_x_y = sum_coproduct / scores1.length;
        result = cov_x_y / (pop_sd_x*pop_sd_y);
        return result;
    }
}