[SciPy-User] Interpolate: Derivatives of parametric splines

[Raimund Andersen]

Hello Zach,

once again thank you so much for your long and detailed answer.

After testing this with many different kinds of input data, I really like it. Of course you are right, parametric splines are much less exact near the endpoints compared to the nonparametric ones. I didn't thought about that.
Indeed, with 20 points of input data, even the second derivative is about 0 near the endpoints, and I am mainly interested in finding the zeros of the second derivative, so here I don't care much about how the slope goes in between.
Maybe I can make use of the difference between x and (dx/du*u) as a kind of fuzzy quality rate; comparing (dx/du) between the first and the second derivative could bring some insights, too. 

This was really the help I needed, also thanks to you, Warren.

Raimund
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