I have code interpolating a spline from a CDF that seems valid between the range x=40 and x=110. Below 40, I want a flat line at 0, and after 110, a flat line at 1 towards infinite. I have come up with this code: def _find_spline(x_orig: np.ndarray, cdf: np.ndarray) -> BSpline: # Find the smoothing factor smoothing_factor, iters = _find_highest_smoothing_factor(x_orig, cdf, 1e-5) # Fit a linear spline to the first segment t_begin, c_begin, k_begin = splrep([0, x_orig[0]], [0, cdf[0]], k=1) # Fit the middle segment with the specified smoothing factor t_middle, c_middle, k_middle = splrep(x_orig, cdf, s=smoothing_factor) # Explicitly construct the final segment t_end = np.array([x_orig[-1], x_orig[-1], 300, 300]) # Linear knots c_end = np.array([cdf[-1], 1.0]) # Start from the evaluated value # Combine the knots and coefficients t_combined = np.concatenate([t_begin[:-1], t_middle[1:-1], t_end]) c_combined = np.concatenate([c_begin[:-1], c_middle[1:-1], c_end]) return BSpline(t_combined, c_combined, k_middle, extrapolate=True) however, this generates something like in: so, the first segment until 40 seems fine and evaluates to 0... but I don't know why the spline goes down to 0 at the end at 110, I want it just to continue straight... What is wrong? Continue reading...
