On Tue, Aug 4, 2020 at 6:10 PM Charles R Harris <charlesr.har...@gmail.com> wrote:
> > > On Tue, Aug 4, 2020 at 4:55 AM Ralf Gommers <ralf.gomm...@gmail.com> > wrote: > >> >> >> On Tue, Aug 4, 2020 at 1:49 AM Chris Vavaliaris <cv1...@wildcats.unh.edu> >> wrote: >> >>> 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. >> >> > Chebfun <https://github.com/chebfun/chebfun> is based around this method, > they use series with possibly thousands of terms. Trefethen is a big fan of > Chebyshev polynomials. > I am quite sure that Chebyshev transforms are useful, but it does feel like something more directly suitable for SciPy than NumPy. The current division for submodules like numpy.fft/scipy.fft and numpy.linalg/scipy.linalg exists for outdated historical reasons, but at this point it is easiest for users to understand if has SciPy has a strict superset of NumPy's functionality here. Chuck > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion >
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