if(layerNr == weightMatrixesLength - 1) // OutputLayer
{
    const errorMatrix = Matrix.fromArray(pExpectedOutput);
    errorMatrix.subtract(this.netValueMatrixes[layerNr + 1]);

    deltaMatrix.multiplyM(errorMatrix);
    deltaMatrix.multiply(pTrainingConstant);

    this.deltaMatrixes[layerNr] = deltaMatrix;

    /*
        Note the difference between weight matrixes and bias matrixes
    */
    this.weightMatrixes[layerNr].add(Matrix.multiply(deltaMatrix, Matrix.transpose(this.netValueMatrixes[layerNr])));
    this.biasMatrixes[layerNr].add(deltaMatrix);
} else // HiddenLayer
{
    const deltaSumMatrix = Matrix.multiply(Matrix.transpose(this.weightMatrixes[layerNr + 1]),
    this.deltaMatrixes[layerNr + 1]);

    deltaMatrix.multiplyM(deltaSumMatrix);
    deltaMatrix.multiply(pTrainingConstant);

    this.deltaMatrixes[layerNr] = deltaMatrix;

    /*
        Note the difference between weight matrixes and bias matrixes
    */
    this.weightMatrixes[layerNr].add(Matrix.multiply(deltaMatrix, Matrix.transpose(this.netValueMatrixes[layerNr])));

    this.biasMatrixes[layerNr].add(deltaMatrix);
}