/**
* 15.
* @brief Extract the diagonal elements of a matrix.
* @param[in] A The (square) matrix whose diagonal is to be extracted.
* @param[out] B A diagonal matrix containing entries from A.
*/
static void diag(const matrix_type& A,
matrix_type& B) {
/* create a zeros matrix of the right dimension and assign to B */
const int n = A.Width();
B = zeros(n, n);
/* Set the diagonals of B */
for (int i=0; i<n; ++i) B.Set(i, i, A.Get(i,i));
}
/**
* 17.
* @brief Multiply one scalar with matrix.
* @param[in] A The matrix.
* @param[in] a The scalar.
* @param[out] B B is overwritten with (A*B).
*/
static void multiply(const matrix_type& A,
const value_type& a,
matrix_type& B) {
/** Result matrices should always be of the right size */
B.Resize(A.Height(), A.Width());
/** Get the matrix dimensions. */
const int m = A.Height();
const int n = A.Width();
/** Simple scalar-matrix product. */
for (int i=0; i<m; ++i)
for (int j=0; j<n; ++j)
B.Set(i, j, (a*A.Get(i, j)));
}
/**
* 16.
* @brief Compute the element-wise product of two matrices.
* @param[in] A the first matrix.
* @param[in] B the second matrix.
* @param[out] C the result, which contains A.*B.
*/
static void elementwiseProduct(const matrix_type& A,
const matrix_type& B,
matrix_type& C) {
/** Result matrices should always be of the right size */
C.Resize (A.Height(), A.Width());
/* Get the matrix dimensions */
const int m = A.Height();
const int n = A.Width();
/* Simple element-wise product */
for (int i=0; i<m; ++i)
for (int j=0; j<n; ++j)
C.Set(i, j, (A.Get(i,j)*B.Get(i,j)));
}