// implement the function fit_least_squares
public Box<double[][], Double, Matrix> fit_least_squares(double[][] points, Function[] f) {
Box<double[][], Double, Matrix> container = new Box<double[][], Double, Matrix>();
int prow = points.length;
int flen = f.length;
Matrix A = new Matrix(prow, flen);
Matrix b = new Matrix(prow, 1);
for (int i = 0; i < prow; i++) {
double weight = 0.0;
if (points[i].length > 2) {
weight = 1.0 / points[i][2];
} else {
weight = 1.0;
}
double val = weight * points[i][1];
b.setitem(i, 0, val);
for (int j = 0; j < flen; j++) {
double val2 = weight * f[j].apply(points[i][0]);
A.setitem(i, j, val2);
}
}
Matrix c = ((A.transpose().mul(A)).inverse()).mul(A.transpose().mul(b));
Matrix chi = A.mul(c).add(b.neg());
double chi2 = Math.pow(chi.norm(2), 2);
double x = 1.0;
Matrix fitting_f = eval_fitting_function(f, c, x);
container.setT(c.as_list());
container.setU(chi2);
container.setV(fitting_f);
return container;
}
