/**
* <p>
* Performs the following operation:<br>
* <br>
* B = A + αI
* <p>
*
* @param A A square matrix. Not modified.
* @param B A square matrix that the results are saved to. Modified.
* @param alpha Scaling factor for the identity matrix.
*/
public static void addIdentity(FMatrix1Row A, FMatrix1Row B, float alpha)
{
if (A.numCols != A.numRows)
{
throw new ArgumentException("A must be square");
}
if (B.numCols != A.numCols || B.numRows != A.numRows)
{
throw new ArgumentException("B must be the same shape as A");
}
int n = A.numCols;
int index = 0;
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++, index++)
{
if (i == j)
{
B.set(index, A.get(index) + alpha);
}
else
{
B.set(index, A.get(index));
}
}
}
}
/**
* <p>
* Extracts a row or column vector from matrix A. The first element in the matrix is at element (rowA,colA).
* The next 'length' elements are extracted along a row or column. The results are put into vector 'v'
* start at its element v0.
* </p>
*
* @param A Matrix that the vector is being extracted from. Not modified.
* @param rowA Row of the first element that is extracted.
* @param colA Column of the first element that is extracted.
* @param length Length of the extracted vector.
* @param row If true a row vector is extracted, otherwise a column vector is extracted.
* @param offsetV First element in 'v' where the results are extracted to.
* @param v Vector where the results are written to. Modified.
*/
public static void subvector(FMatrix1Row A, int rowA, int colA, int length, bool row, int offsetV,
FMatrix1Row v)
{
if (row)
{
for (int i = 0; i < length; i++)
{
v.set(offsetV + i, A.get(rowA, colA + i));
}
}
else
{
for (int i = 0; i < length; i++)
{
v.set(offsetV + i, A.get(rowA + i, colA));
}
}
}
public static void setSubMatrix(FMatrix1Row src, FMatrix1Row dst,
int srcRow, int srcCol, int dstRow, int dstCol,
int numSubRows, int numSubCols)
{
for (int i = 0; i < numSubRows; i++)
{
for (int j = 0; j < numSubCols; j++)
{
float val = src.get(i + srcRow, j + srcCol);
dst.set(i + dstRow, j + dstCol, val);
}
}
}
/**
* <p>
* Sets A ∈ ℜ <sup>m × n</sup> equal to an outer product multiplication of the two
* vectors. This is also known as a rank-1 operation.<br>
* <br>
* A = x * y'
* where x ∈ ℜ <sup>m</sup> and y ∈ ℜ <sup>n</sup> are vectors.
* </p>
* <p>
* Which is equivalent to: A<sub>ij</sub> = x<sub>i</sub>*y<sub>j</sub>
* </p>
*
* <p>
* These functions are often used inside of highly optimized code and therefor sanity checks are
* kept to a minimum. It is not recommended that any of these functions be used directly.
* </p>
*
* @param x A vector with m elements. Not modified.
* @param y A vector with n elements. Not modified.
* @param A A Matrix with m by n elements. Modified.
*/
public static void outerProd(FMatrixD1 x, FMatrixD1 y, FMatrix1Row A)
{
int m = A.numRows;
int n = A.numCols;
int index = 0;
for (int i = 0; i < m; i++)
{
float xdat = x.get(i);
for (int j = 0; j < n; j++)
{
A.set(index++, xdat * y.get(j));
}
}
}