diff --git a/src/Function2D.cpp b/src/Function2D.cpp
index d522cb9..f0a395a 100644
--- a/src/Function2D.cpp
+++ b/src/Function2D.cpp
@@ -134,9 +134,11 @@ Matrix Aurora::std(const Matrix &aMatrix) {
     int calc_size = src.getDimSize(0) == 1 ? src.getDimSize(1) : src.getDimSize(0);
     int col = src.getDimSize(0) == 1?1:src.getDimSize(1) ;
     auto std = Aurora::malloc(col);
+    auto meanM = Aurora::mean(aMatrix);
     for (int i = 0; i < col; ++i) {
         double *p = src.getData() + i * calc_size;
-        double mean = cblas_dasum(calc_size, p, 1) / calc_size;
+        
+        double mean = meanM[i];
         vdSubI(calc_size, p, 1, &mean, 0, p, 1);
         vdSqr(calc_size, p, p);
         std[i] = cblas_dasum(calc_size, p, 1) / (calc_size - 1);