code: public static double meanCenter(DenseMatrix64F points, DenseMatrix64F center)
      {
          assert points.numCols == 2;
          assert center.numCols == 1;
          assert center.numRows == 2;
          center.zero();
          int count = points.numRows;
          double[] d = points.data;
          for (int i=0;i<count;i++)
          {
              center.add(0, 0, d[2*i]);
              center.add(1, 0, d[2*i+1]);
          }
          if (count > 0)
          {
              divide(center, count);
              DenseMatrix64F di = new DenseMatrix64F(points.numRows, 1);
              computeDi(center, points, di);
              return elementSum(di) / (double)points.numRows;
          }
          else
          {
              return Double.NaN;
          }
      }
docs: Calculates mean tempCenter of points
  @param points in
  @param center out
  @return