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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; } }