Thanks for the explanation. I see the point now.
On Thu, Mar 17, 2016 at 3:21 PM, Nathaniel Smith <n...@pobox.com> wrote: > On Thu, Mar 17, 2016 at 2:04 PM, Feng Yu <rainwood...@gmail.com> wrote: >> Hi, >> >> ang2pix is used in astronomy to pixelize coordinate in forms of >> (theta, phi). healpy is a binding of healpix >> (http://healpix.sourceforge.net/, introduction there too), plus a lot >> of more extra features or bloat (and I am not particular fond of this >> aspect of healpy). It gets the work done. >> >> You can think of the function ang2pix as nump.digitize for angular input. >> >> 'nside' and 'nest' controls the number of pixels and the ordering of >> pixels (since it is 2d to linear index). >> >> The important thing here is ang2pix is a pure function from (nside, >> nest, theta, phi) to pixelid, so in principle it can be written as a >> ufunc to extend the functionality to generate pixel ids for different >> nside and nest settings in the same function call. > > Thanks for the details! > > From what you're saying, it sounds like ang2pix actually wouldn't care > either way about the gufunc broadcasting changes we're talking about. > When we talk about *g*eneralized ufuncs, we're referring to ufuncs > where the "core" minimal operation that gets looped over is already > intrinsically something that operates on arrays, not just scalars -- > so operations like matrix multiply, sum, mean, mode, sort, etc., which > you might want to apply simultaneously to a whole bunch of arrays, and > the question is about how to handle these "inner" dimensions. In this > case it sounds like (nside, nest, theta, phi) are 4 scalars, right? So > this would just be a regular ufunc, and the whole issue doesn't arise. > Broadcast all you like :-) > > -n > > -- > Nathaniel J. Smith -- https://vorpus.org > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > https://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org https://mail.scipy.org/mailman/listinfo/numpy-discussion
