Add monotonic cubic spline (PCHIP) interpolation#335
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josevalim merged 1 commit intoJul 11, 2026
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Adds Scholar.Interpolation.MonotonicCubicSpline, a piecewise cubic Hermite interpolant whose knot derivatives are chosen with the Fritsch-Carlson method so the curve stays monotonic where the data is monotonic and does not overshoot around local extrema (equivalent to scipy.interpolate.PchipInterpolator). The power-basis coefficient layout and predict/3 are shared with CubicSpline, so only the derivative computation differs. Reference values in the tests were taken from SciPy. Closes elixir-nx#322
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Adds Scholar.Interpolation.MonotonicCubicSpline, a piecewise cubic Hermite interpolant whose knot derivatives are chosen with the Fritsch-Carlson method so the curve stays monotonic where the data is monotonic and does not overshoot around local extrema (equivalent to scipy.interpolate.PchipInterpolator).
The power-basis coefficient layout and predict/3 are shared with CubicSpline, so only the derivative computation differs. Reference values in the tests were taken from SciPy.
Closes #322