Add correlation as distance

Parallel_Algorithm/shared/math_util.c

@@ -7,3 +7,19 @@ float distance(int N_features,float *x1,float *x2){
  dist += (x1[j]-x2[j])*(x1[j]-x2[j]);
  return(dist);
 }
+
+float correlation(int N_features,float *x,float *y){
+ float xsum=0.0,ysum=0.0,xysum=0.0,xsqr_sum=0.0,ysqr_sum=0.0;
+ for (int j = 0; j<N_features; j++) {
+ xsum = xsum + x[i];
+ ysum = ysum + y[i];
+ xysum = xysum + x[i] * y[i];
+ xsqr_sum = xsqr_sum + x[i] * x[i];
+ ysqr_sum = ysqr_sum + y[i] * y[i];
+ }
+
+ float num = ((N_features * xysum) - (xsum * ysum));
+ float deno = ((N_features * xsqr_sum - xsum * xsum)* (N_features * ysqr_sum - ysum * ysum));
+ float coeff = num / sqrt(deno);
+ return(coeff);
+}