Module least_squares 

Polynomial least-squares fitting via the normal equations (VᵀV) c = Vᵀy, solved by Gaussian elimination with partial pivoting (the small (d+1)×(d+1) system).

Functions

poly_eval

Evaluate a polynomial given ascending coefficients at x (Horner).

poly_fit

Fit a degree-degree polynomial to (xs, ys) in the least-squares sense. Returns coefficients in ascending order [c₀, c₁, …, c_degree] (so the polynomial is Σ cₖ xᵏ). Fails closed if there are too few points or the system is singular.