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. There are probably functions in numpy that can benefit from this as well, but I can't immediately think of any. Yu On Thu, Mar 17, 2016 at 8:09 AM, Joseph Fox-Rabinovitz <jfoxrabinov...@gmail.com> wrote: > On Thu, Mar 17, 2016 at 10:03 AM, Nathaniel Smith <n...@pobox.com> wrote: >> On Mar 17, 2016 1:22 AM, "Feng Yu" <rainwood...@gmail.com> wrote: >>> >>> Hi, >>> >>> Here is another example. >>> >>> To write pix2ang (and similar functions) to a ufunc, one may want to have >>> implicit scalar broadcast on `nested` and `nsides` arguments. >>> >>> The function is described here: >>> >>> >>> http://healpy.readthedocs.org/en/latest/generated/healpy.pixelfunc.pix2ang.html#healpy.pixelfunc.pix2ang >> >> Sorry, can you elaborate on what that function does, maybe give an example, >> for those of us who haven't used healpy before? I can't quite understand >> from that page, but am interested... >> >> -n > > Likewise. I just took a look at the library and it looks fascinating. > I might just use it for something fun to learn about it. > > -Joe > _______________________________________________ > 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
