public static NMatrix Minors(NMatrix matrix)
{
NMatrix minors = new NMatrix(new decimal[matrix.Rows, matrix.Columns]);
for (int i = 0; i < matrix.Rows; i++)
{
for (int j = 0; j < matrix.Columns; j++)
{
if (matrix.Rows - 1 > 0 && matrix.Columns - 1 > 0)
{
NMatrix minorCalc = new NMatrix(new decimal[matrix.Rows - 1, matrix.Columns - 1]);
int x0 = 0;
for (int x = 0; x < matrix.Rows; x++)
{
if (x == i)
{
x++;
}
if (x == matrix.Rows)
{
break;
}
int y0 = 0;
for (int y = 0; y < matrix.Columns; y++)
{
if (y == j)
{
y++;
}
if (y == matrix.Columns)
{
break;
}
minorCalc.Data[x0, y0] = matrix.Data[x, y];
y0++;
}
x0++;
}
minors.Data[i, j] = NMatrix.Determinant(minorCalc);
}
else if (matrix.Rows == 1 && matrix.Columns == 1)
{
minors.Data[i, j] = matrix.Data[i, j];
}
else
{
throw new ArgumentException("A minor can only be calculated for a square matrix.");
}
}
}
return(minors);
}
public static NMatrix Cofactors(NMatrix matrix)
{
NMatrix minors = NMatrix.Minors(matrix);
for (int i = 0; i < matrix.Rows; i++)
{
for (int j = 0; j < matrix.Columns; j++)
{
minors.Data[i, j] *= (Tools.Validators.IsEven(i + j)) ? 1 : -1;
}
}
return(minors);// Now holds cofactors
}
public static decimal Determinant(NMatrix matrix)
{
if (matrix.Rows != matrix.Columns)
{
throw new ArgumentException("Determinant calculation failed - the matrix wasn't square.");
}
decimal result = 0;
if (matrix.Rows == 0)
{
}
else if (matrix.Rows == 1)
{
result = matrix.Data[0, 0];
}
else
{
NMatrix cfs;
try
{
cfs = NMatrix.Cofactors(matrix);
}
catch (ArgumentException)
{
// IS THIS CORRECT?!
throw new ArgumentException("Determinant calculation failed - this was likely because its determinant was undifined.");
}
for (int i = 0; i < matrix.Columns; i++)
{
result += matrix.Data[0, i] * cfs.Data[0, i];
}
}
return(result);
}
public IMatrix AdjointMatrix()
{
return(NMatrix.Adjoint(this));
}
public NMatrix Adjoint()
{
return(NMatrix.Adjoint(this));
}
public static NMatrix Adjoint(NMatrix matrix)
{
return(matrix.Cofactors().T());
}
public decimal Determinant()
{
return(NMatrix.Determinant(this));
}
public IMatrix CofactorsMatrix()
{
return(NMatrix.Cofactors(this));
}
public IMatrix MinorsMatrix()
{
return(NMatrix.Minors(this));
}
public NMatrix Minors()
{
return(NMatrix.Minors(this));
}