public static MatrixNxN Transpose(MatrixNxN _A)
{
if (_A == null || !_A.is_valid)
{
return(_A);
}
int nR = _A.nr_rows;
int nC = _A.nr_cols;
int nE = _A.nr_entries;
double[] vals = _A.values;
double[] new_vals = new double[nE];
// a b c d e f -> a d b e c f
//---------------------------
// a b c -> a d
// d e f b e
// c f
int counter = 0;
for (int j = 0; j < nC; j++)
{
for (int i = j; i < nE && counter < nE; i += nC, counter++)
{
new_vals[counter] = vals[i];
}
}
return(new MatrixNxN(nC, nR, new_vals));
}
// A'x A
public static MatrixNxN Squared(MatrixNxN _A)
{
if (_A == null || !_A.is_valid)
{
return(MatrixNxN.ONEVALUE);
}
int nR = _A.nr_rows;
int nC = _A.nr_cols;
int nE = _A.nr_entries;
double[] vals = _A.values;
double[] calc = new double[nC * nC];
double[,] rowsA = new double[nR, nC];
double[,] colsA = new double[nC, nR];
// extract the rows of A
for (int i = 0; i < nR; i++)
{
for (int j = 0; j < nC; j++)
{
rowsA[i, j] = vals[i * nC + j];
}
}
// extract the columns of A
for (int j = 0; j < nC; j++)
{
for (int i = j, counter = 0; i < nE && counter < nR; i += nC, counter++)
{
colsA[j, counter] = vals[i];
}
}
// perform calculation
for (int i = 0; i < nC; i++)
{
for (int j = 0; j < nC; j++)
{
calc[i * nC + j] = 0;
for (int k = 0; k < nR; k++)
{
calc[i * nC + j] += colsA[i, k] * colsA[j, k];
}
}
}
return(new MatrixNxN(nC, nC, calc));
}