public double Determinant()
{
if (Width != Height)
{
return(0.0);
}
DMatrix result = DMatrixUtility.UnitVector2d(Height);
DMatrix clone = Clone();
int max;
double tmp = 0.0;
int i, j, k;
for (k = 0; k < Height; k++)
{
max = k;
for (j = k + 1; j < Height; j++)
{
if (Math.Abs(clone[j, k]) > Math.Abs(clone[max, k]))
{
max = j;
}
}
if (max != k)
{
for (i = 0; i < Width; i++)
{
(clone[max, i], clone[k, i]) = (clone[k, i], clone[max, i]);
(result[max, i], result[k, i]) = (result[k, i], result[max, i]);
}
}
tmp = clone[k, k];
}
return(tmp);
}
/// <summary>
/// 逆行列を計算する。
/// 実装は以下のページを参考（https://qiita.com/sekky0816/items/8c73a7ec32fd9b040127）
/// TODO https://docs.microsoft.com/ja-jp/archive/msdn-magazine/2012/december/csharp-matrix-decomposition#%E8%A1%8C%E5%88%97%E5%BC%8F も参考にして組み込む
/// </summary>
/// <returns></returns>
public DMatrix Inv()
{
if (Width != Height)
{
return(null);
}
DMatrix result = DMatrixUtility.UnitVector2d(Height);
DMatrix clone = Clone();
int max;
double tmp;
int i, j, k;
for (k = 0; k < Height; k++)
{
max = k;
for (j = k + 1; j < Height; j++)
{
if (Math.Abs(clone[j, k]) > Math.Abs(clone[max, k]))
{
max = j;
}
}
if (max != k)
{
for (i = 0; i < Width; i++)
{
(clone[max, i], clone[k, i]) = (clone[k, i], clone[max, i]);
(result[max, i], result[k, i]) = (result[k, i], result[max, i]);
}
}
tmp = clone[k, k];
for (i = 0; i < Width; i++)
{
clone[k, i] /= tmp;
result[k, i] /= tmp;
}
for (j = 0; j < Height; j++)
{
if (j != k)
{
tmp = clone[j, k] / clone[k, k];
for (i = 0; i < Width; i++)
{
clone[j, i] -= clone[k, i] * tmp;
result[j, i] -= result[k, i] * tmp;
}
}
}
}
for (j = 0; j < Height; j++)
{
for (i = 0; i < Width; i++)
{
if (double.IsNaN(result[j, i]))
{
return(null);
}
}
}
return(result);
}
public DMatrix(int height, int width)
{
this.Mat = DMatrixUtility.Zeros2d(height, width).Mat;
this.Height = height;
this.Width = width;
}
