Source code for dustmaps.healpix_map

#!/usr/bin/env python
# A set of HEALPix map classes.
# Copyright (C) 2016  Gregory M. Green
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# GNU General Public License for more details.
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

from __future__ import print_function, division

import healpy as hp
import as fits

from .map_base import DustMap, coord2healpix

[docs]class HEALPixQuery(DustMap): """ A class for querying HEALPix maps. """
[docs] def __init__(self, pix_val, nest, coord_frame): """ Args: pix_val (array): Value of the map in every pixel. The length of the array must be of the form `12 * nside**2`, where `nside` is a power of two. nest (bool): `True` if the map uses nested ordering. `False` if ring ordering is used. coord_frame (str): The coordinate system that the HEALPix map is in. Should be one of the frames supported by `astropy.coordinates`. """ self._nside = hp.pixelfunc.npix2nside(len(pix_val)) self._pix_val = pix_val self._nest = nest self._frame = coord_frame super(HEALPixQuery, self).__init__()
[docs] def query(self, coords): """ Args: coords (`astropy.coordinates.SkyCoord`): The coordinates to query. Returns: A float array of the value of the map at the given coordinates. The shape of the output is the same as the shape of the coordinates stored by `coords`. """ pix_idx = coord2healpix(coords, self._frame, self._nside, nest=self._nest) return self._pix_val[pix_idx]
[docs]class HEALPixFITSQuery(HEALPixQuery): """ A HEALPix map class that is initialized from a FITS file. """
[docs] def __init__(self, fname, coord_frame, hdu=0, field=None, dtype='f8'): """ Args: fname (str, HDUList, TableHDU or BinTableHDU): The filename, HDUList or HDU from which the map should be loaded. coord_frame (str): The coordinate system in which the HEALPix map is defined. Must be a coordinate frame which `astropy` understands. hdu (Optional[int or str]): Specifies which HDU to load the map from. Defaults to `0`. field (Optional[int or str]): Specifies which field (column) to load the map from. Defaults to `None`, meaning that `[:]` is used. dtype (Optional[str or type]): The data will be coerced to this datatype. Can be any type specification that numpy understands. Defaults to `'f8'`, for IEEE754 double precision. """ if isinstance(fname, basestring): close_file = True hdulist = print( hdu = hdulist[hdu] elif isinstance(fname, fits.HDUList): hdu = fname[hdu] elif (isinstance(fname, fits.TableHDU) or isinstance(fname, fits.BinTableHDU)): hdu = fname else: raise TypeError('`fname` must be a `str`, `HDUList`, `TableHDU` or ' '`BinTableHDU`.') if field is None: pix_val =[:].ravel().astype(dtype) else: pix_val =[field][:].ravel().astype(dtype) nest = hdu.header.get('ORDERING', 'NESTED').strip() == 'NESTED' if close_file: hdulist.close() super(HEALPixFITSQuery, self).__init__(pix_val, nest, coord_frame)