code: private void PowerSpectrum() {
          Power = new double[data.length][data[0].length];
          PowerMax = 0;
  
          for (int i = 0; i < data.length; i++) {
              for (int j = 0; j < data[0].length; j++) {
                  double p = data[i][j];
                  if (p < 0) p = -p;
                  Power[i][j] = p;
                  if (p > PowerMax) PowerMax = p;
              }
          }
      }
docs: compute the Power Spectrum;