PR #16999: https://github.com/numpy/numpy/pull/16999
Hello all,
this PR adds the two 1D Chebyshev transform functions `chebyfft` and
`ichebyfft` into the `numpy.fft` module, utilizing the real FFTs `rfft` and
`irfft`, respectively. As far as I understand, `pockefft` does not support
cosine transforms natively; for this reason, an even extension of the input
vector is constructed, whose real FFT corresponds to a cosine transform.
The motivation behind these two additions is the ability to quickly perform
direct and inverse Chebyshev transforms with `numpy`, without the need to
write scripts that do the necessary (although minor) modifications.
Chebyshev transforms are used often e.g. in the spectral integration of PDE
problems; thus, I believe having them implemented in `numpy` would be useful
to many people in the community.
I'm happy to get comments/feedback on this feature, and on whether it's
something more people would be interested in. Also, I'm not entirely sure
what part of this functionality is/isn't present in `scipy`, so that the two
`fft` modules remain consistent with one another.
Hi Chris, that's a good question. scipy.fft is a superset of numpy.fft, and the functionality included in NumPy is really only the basics that are needed in many fields. The reason for the duplication stems from way back when we had no wheels and SciPy was very hard to install. So I don't think there's anything we'd add to numpy.fft at this point.
As I commented on your PR, it would be useful to add some references and applications, and then make your proposal on the scipy-dev list.