diagonal method
Passing in an m x n array, returns an array with only the main diagonals, all the rest are zeros
Implementation
List<List<double>> diagonal(List<List<double>> arr) {
int nrows = arr.length;
int ncols = arr[0].length;
List<List<double>> out;
out = numeric.createMatrix(nrows, ncols, 0.0);
for (int i = 0; i < nrows; i++) {
for (int j = 0; j < ncols; j++) {
if (i == j) {
out[i][j] = arr[i][j];
}
}
}
return out;
}