private static SparseRealMatrix initializeMatrix(SparseRealMatrix matrix, double sigma) {
NormalDistribution normRandom = new NormalDistribution(0.0, sigma);
int r = matrix.getRowDimension();
int c = matrix.getColumnDimension();
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++) {
double x = normRandom.sample();
matrix.setEntry(i, j, x);
}
}
return matrix;
}
