public MatrixNxM GetInverse()
{
if (Rows != Columns)
{
throw new MatrixDimensionExceptionNonSquare(this);
}
double det = this.GetDeterminant();
MatrixNxM inv = new MatrixNxM(Rows, Columns);
for (int x = 0; x < Columns; x++)
{
for (int y = 0; y < Rows; y++)
{
MatrixNxM sub = this.GetSubmatrix(x, y);
int f1 = (x % 2 == 0) ? 1 : -1;
int f2 = (y % 2 == 0) ? 1 : -1;
inv[y, x] = f1 * f2 * sub.GetDeterminant() / det;
}
}
return(inv);
}
public double GetDeterminant()
{
if (Rows != Columns)
{
throw new MatrixDimensionExceptionNonSquare(this);
}
if (Rows == 0 && Columns == 0)
{
return(0);
}
if (Rows == 1 && Columns == 1)
{
return(this[0, 0]);
}
if (Rows == 2 && Columns == 2)
{
return(this[0, 0] * this[1, 1] - this[0, 1] * this[1, 0]);
}
double sum = 0;
for (int i = 0; i < Columns; i++)
{
if (this[0, i] == 0)
{
continue;
}
MatrixNxM sub = this.GetSubmatrix(0, i);
int factor = (i % 2 == 0) ? 1 : -1;
sum += factor * this[0, i] * sub.GetDeterminant();
}
return(sum);
}
