Cubic spline fitting options need improvement

[Andrew_Smith]

We use shape preserving spline curves a lot but find the Akima offering in MKL has some shortcomings.

a) The ends of the spline are very flat. There are some modified Akima schemes which improve this aspect. One is offered in Boost for free and another in Alglib and other commercial packages.

b) The Akima spline does not have continuous second derivative. The one we use where we need this inserts additional breakpoints to preserve the shape (monotonicity).

[Gennady_F_Intel]

Thanks Andrew. We will add this topic to the future schedule.

[Andrey_F_Intel]

Hi Andrew. Sorry for the delay.

Regarding a). Could you please add more information about the use case?

It would be ideal if you shared the dataset (x, y, sites) when you see flat ends of the Akima spline (if possible).

The thing is that we don't see any issues with our datasets.

[Andrey_F_Intel]

@Andrew_Smith, please, let us know if the issue is still relevant

[Andrew_Smith]

I am happy to close this. I find the the MKL Akima spline with Not-A-Knot end option suites my needs. It models a radius as well as the Alglib Akima spline.