Derivative of Spline Surface

[BenMichell]

Hi Eugene,

I came across your package trying to replicate some analysis that had been done in Matlab using csaps. The tool works perfectly, however the analysis I'm replicating used the Matlab function fnders to return the derivative of the spline surface fitted using csaps.

Is there a way to do this in your package, or is it something you would consider as an additional feature?

Many thanks again for the tool.

Best Regards,

Ben

[espdev]

Hi Ben,

Currently, csaps package does not provide any spline analysis functionality. However, I think we can convert csaps PP spline representation to scipy PPoly object for univariate/multivariate cases and NdPPoly for nd-grid cases. scipy PPoly class contains spline analysis methods (derivative, integrate, ...) and we just can use this functionality for csaps splines because it is regular cubic spline with natural boundary condition.

I can try to implement converting SplinePPForm to PPoly. In fact, we just need to reshape the array of spline coefficients and use PPoly.construct_fast method.

[BenMichell]

Hi Eugene, Thanks for the reply. I will need to do a bit of work to understand what to do, but it sounds positive. I think I'm struggling with the fact that the documentation examples in SciPy aren't immediately obviously what I need. I will take a look. Best Regards, Ben

…

On Tue, 2 Jun 2020 at 13:01, Eugene Prilepin ***@***.***> wrote: Hi Ben, Currently, csaps package do not provide any spline analysis functionality. However, I think we can convert csaps PP spline representation to scipy PPoly <https://docs.scipy.org/doc/scipy/reference/generated/scipy.interpolate.PPoly.html#scipy.interpolate.PPoly> object for univariate/multivariate cases and NdPPoly <https://docs.scipy.org/doc/scipy/reference/generated/scipy.interpolate.NdPPoly.html#scipy.interpolate.NdPPoly> for nd-grid cases. scipy PPoly class contains spline analysis methods (derivative, integrate, ...) and we just can use this functionality for csaps splines because it is regular cubic splines with natural boundary condition. I can try to implement converting SplinePPForm to PPoly. In fact, we just need to reshape the array of spline coefficients and use PPoly.construct_fast method. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#20 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AMO5QIDBD2HPHFGCPDXNSL3RUTSZDANCNFSM4NQSAHWQ> .

[Taniya-Fansupkar]

Hi Eugene,
I am looking for finding un normalized taylor coefficient which is returned by fntlr function in Matlab and the fntlr takes input spline object returned by csaps in Matlab. How can I do similar thing using your library of csaps

[Taniya-Fansupkar]

Same as Ben who is looking for fnder for finding derivative, I am looking for fntlr equivalent for finding unnormalized Taylor coefficient

[espdev]

@Taniya-Fansupkar,

It seems to me fntlr function and its analogues do not exist in scipy in some form. You can implement the function for a cubic spline. I have not looked at the fntlr matlab source code yet and do not know how difficult it is.

I want to add support of analysis functionality to csaps package based on scipy PPoly class. We could add fntlr also.

[Taniya-Fansupkar]

@espdev
It would be much more beneficial if you add support for analysis functionality to csaps package.

[espdev]

@BenMichell @Taniya-Fansupkar

Spline analysis functionality has been implemented via SciPy PPoly/NdPPoly classes. These changes already in master branch and will be in 1.0.0 release. See tests/test_analysis how to use it.

Also I try to implement and add fntlr to 1.0.0 release or 1.1.0.