R method
Return the upper triangular factor R
Implementation
Array2d R() {
var R = Array2d.fixed(_n, _n);
for (var i = 0; i < _n; i++) {
for (var j = 0; j < _n; j++) {
if (i < j) {
R[i][j] = _QR[i][j];
} else if (i == j) {
R[i][j] = _Rdiag[i];
} else {
R[i][j] = 0.0;
}
}
}
return R;
}