code: public static void fillGaussian(DMatrixD1 mat , double mean , double stdev , Random rand )
      {
          double d[] = mat.getData();
          int size = mat.getNumElements();
  
          for( int i = 0; i < size; i++ ) {
              d[i] = mean + stdev * (double)rand.nextGaussian();
          }
      }
docs: <p>
  Sets each element in the matrix to a value drawn from an Gaussian distribution with the specified mean and
  standard deviation
  </p>
  
  @param mat The matrix who is to be randomized. Modified.
  @param mean Mean value in the distribution
  @param stdev Standard deviation in the distribution
  @param rand Random number generator used to fill the matrix.