/// <summary>
/// Method is used to get a determinant of the required matrix.
/// </summary>
/// <param name="matrix">Initial matrix to get determinant.</param>
/// <returns>Matrix determinant.</returns>
public static double GetMatrixDeterminant(MatrixT <T> matrix)
{
if (matrix.Elements.Length == 1)
{
return((dynamic)matrix[0, 0]);
}
if (matrix.Elements.Length == 4)
{
return((dynamic)matrix[0, 0] * (dynamic)matrix[1, 1] - (dynamic)matrix[0, 1] * (dynamic)matrix[1, 0]);
}
double sign = 1;
double result = 0;
for (int i = 0; i < matrix.Elements.GetLength(1); i++)
{
T[,] minor = MatrixT <T> .GetMinor(matrix.Elements, i);
result += sign * (dynamic)matrix[0, i] * GetMatrixDeterminant(new MatrixT <T>(minor));
sign = -sign;
}
return(result);
}
/// <summary>
/// Method is used to take inversed matrix.
/// </summary>
/// <param name="matrix">Initial matrix.</param>
/// <returns>Inversed matrix.</returns>
public static MatrixT <T> GetInverseMatrix(MatrixT <T> matrix)
{
double determinant = MatrixT <T> .GetMatrixDeterminant(matrix);
if (determinant != 0)
{
MatrixT <T> reversedMatrix = new MatrixT <T>(matrix.Rows, matrix.Columns);
for (int i = 0; i < matrix.Rows; i++)
{
for (int j = 0; j < matrix.Columns; j++)
{
MatrixT <T> tempMatrix = MatrixT <T> .GetMinor(matrix, i, j);
reversedMatrix[i, j] = (dynamic)Math.Pow(-1.0, i + j + 2) * (dynamic)MatrixT <T> .GetMatrixDeterminant(tempMatrix) / (dynamic)determinant;
}
}
return(MatrixT <T> .TransponeMatrix(reversedMatrix));
}
return(null);
}
