/** {@inheritDoc} */
  @Override
  public void calculateError(
      ActivationFunction af,
      double[] b,
      double[] a,
      double[] ideal,
      double[] actual,
      double[] error,
      double derivShift,
      double significance) {

    for (int i = 0; i < actual.length; i++) {
      double deriv = af.derivativeFunction(b[i], a[i]) + derivShift;
      error[i] = ((ideal[i] - actual[i]) * significance) * deriv;
    }
  }