/**
* <p>
* Creates a reflector from the provided vector and gamma.<br>
* <br>
* Q = I - γ u u<sup>H</sup><br>
* </p>
*
* @param u A vector. Not modified.
* @param gamma To produce a reflector gamma needs to be equal to 2/||u||.
* @return An orthogonal reflector.
*/
public static ZMatrixRMaj createReflector(ZMatrixRMaj u, double gamma)
{
if (!MatrixFeatures_ZDRM.isVector(u))
{
throw new ArgumentException("u must be a vector");
}
ZMatrixRMaj Q = CommonOps_ZDRM.identity(u.NumElements);
CommonOps_ZDRM.multAddTransB(-gamma, 0, u, u, Q);
return(Q);
}
/**
* <p>
* Creates a reflector from the provided vector.<br>
* <br>
* Q = I - γ u u<sup>T</sup><br>
* γ = 2/||u||<sup>2</sup>
* </p>
*
* @param u A vector. Not modified.
* @return An orthogonal reflector.
*/
public static ZMatrixRMaj createReflector(ZMatrixRMaj u)
{
if (!MatrixFeatures_ZDRM.isVector(u))
{
throw new ArgumentException("u must be a vector");
}
double norm = NormOps_ZDRM.normF(u);
double gamma = -2.0 / (norm * norm);
ZMatrixRMaj Q = CommonOps_ZDRM.identity(u.NumElements);
CommonOps_ZDRM.multAddTransB(gamma, 0, u, u, Q);
return(Q);
}
/**
* <p>
* Extracts the diagonal elements 'src' write it to the 'dst' vector. 'dst'
* can either be a row or column vector.
* <p>
*
* @param src Matrix whose diagonal elements are being extracted. Not modified.
* @param dst A vector the results will be written into. Modified.
*/
public static void extractDiag(ZMatrixRMaj src, ZMatrixRMaj dst)
{
int N = Math.Min(src.numRows, src.numCols);
// reshape if it's not the right size
if (!MatrixFeatures_ZDRM.isVector(dst) || dst.numCols * dst.numCols != N)
{
dst.reshape(N, 1);
}
for (int i = 0; i < N; i++)
{
int index = src.getIndex(i, i);
dst.data[i * 2] = src.data[index];
dst.data[i * 2 + 1] = src.data[index + 1];
}
}