public void normalizeZeroMeanZeroUnitVariance() {
    FloatMatrix columnMeans = getFirst().columnMeans();
    FloatMatrix columnStds = MatrixUtil.columnStdDeviation(getFirst());

    setFirst(getFirst().subiRowVector(columnMeans));
    columnStds.addi(1e-6f);
    setFirst(getFirst().diviRowVector(columnStds));
  }