Coverage for python/lsst/pipe/tasks/associationUtils.py: 19%
44 statements
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« prev ^ index » next coverage.py v6.4.1, created at 2022-06-14 03:30 -0700
1# This file is part of pipe_tasks.
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (https://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
19# You should have received a copy of the GNU General Public License
20# along with this program. If not, see <https://www.gnu.org/licenses/>.
21#
23"""Utilities for interfacing with healpy. Originally implemented in
24http://github.com/LSSTDESC/dia_pipe
25"""
27import healpy as hp
28import numpy as np
31def toIndex(nside, ra, dec):
32 """Return healpix index given ra, dec in degrees
34 Parameters
35 ----------
36 nside : `int`
37 Power of 2 nside healpix resolution.
38 ra : `float`
39 RA in degrees.
40 dec : `float`
41 Declination in degrees
43 Returns
44 -------
45 index : `int`
46 Unique healpix pixel ID containing point RA, DEC at resolution nside.
47 """
48 return hp.pixelfunc.ang2pix(nside, np.radians(-dec + 90), np.radians(ra))
51def toRaDec(nside, index):
52 """Convert from healpix index to ra,dec in degrees
54 Parameters
55 ----------
56 nside : `int`
57 Resolution of healpixel "grid".
58 index : `int`
59 Index of the healpix pixel we want to find the location of.
61 Returns
62 -------
63 pos : `numpy.ndarray`, (2,)
64 RA and DEC of healpix pixel location in degrees.
65 """
66 vec = hp.pix2ang(nside, index)
67 dec = np.rad2deg(-vec[0]) + 90
68 ra = np.rad2deg(vec[1])
69 return np.dstack((ra, dec))[0]
72def eq2xyz(ra, dec):
73 """Convert from equatorial ra,dec in degrees to x,y,z on unit sphere.
75 Parameters
76 ----------
77 ra : `float`
78 RA in degrees.
79 dec : `float`
80 Declination in degrees
82 Returns
83 -------
84 xyz : `numpy.ndarray`, (3,)
85 Float xyz positions on the unit sphere.
86 """
87 phi = np.deg2rad(ra)
88 theta = np.pi/2 - np.deg2rad(dec)
89 sintheta = np.sin(theta)
90 x = sintheta*np.cos(phi)
91 y = sintheta*np.sin(phi)
92 z = np.cos(theta)
93 return np.array([x, y, z])
96def eq2xyzVec(ra, dec):
97 """Convert equatorial ra,dec in degrees to x,y,z on the unit sphere
98 parameters
100 Vectorized version of ``eq2xyz``
102 Parameters
103 ----------
104 ra : array_like, (N,)
105 Array of RA in degrees.
106 dec : array_like, (N,)
107 Declination in degrees
109 Returns
110 -------
111 vec : `numpy.ndarray`, (N,3)
112 Array of unitsphere 3-vectors.
113 """
114 ra = np.array(ra, dtype='f8', ndmin=1, copy=False)
115 dec = np.array(dec, dtype='f8', ndmin=1, copy=False)
116 if ra.size != dec.size:
117 raise ValueError("ra,dec not same size: %s,%s" % (ra.size, dec.size))
119 vec = eq2xyz(ra, dec)
121 return vec
124def convert_spherical(ra, dec):
125 """Convert from ra,dec to spherical coordinates.
127 Used in query_disc.
129 Parameters
130 ----------
131 ra : `float`
132 RA in radians.
133 dec : `float`
134 Declination in radians
135 """
136 return np.dstack([np.cos(dec*np.pi/180)*np.cos(ra*np.pi/180),
137 np.cos(dec*np.pi/180)*np.sin(ra*np.pi/180),
138 np.sin(dec*np.pi/180)])[0]
141def convert_spherical_array(array):
142 """Convert from and a array ra,dec to spherical coordinates.
144 Used in query_disc
146 Parameters
147 ----------
148 array : `numpy.ndarray`, (N, 2)
149 (N, 2) Array of RA, DEC values.
151 Returns
152 -------
153 vecs : `numpy.ndarray`, (N, 3)
154 Vectors on the unit sphere
155 """
156 ra = array[:, 0]
157 dec = array[:, 1]
158 return convert_spherical(ra, dec)
161def query_disc(nside, ra, dec, max_rad, min_rad=0):
162 """Get the list of healpix indices within max_rad, min_rad given in radians
163 around ra,dec given in degrees
165 Parameters
166 ----------
167 nside : `int`
168 Resolution of the healpixels to search/return.
169 ra : `float`
170 RA in degrees.
171 dec : `float`
172 Declination in degrees
173 max_rad : `float`
174 Max distance in radians to search nearby healpixels.
175 min_rad : `float`, optional
176 Minimum distance in radians to search healpixels. Default = 0.
177 """
178 if np.isscalar(ra):
179 ra = np.array([ra])
180 dec = np.array([dec])
182 pixels = np.unique(
183 [hp.query_disc(nside, eq2xyzVec(a, b), max_rad)
184 for (a, b) in zip(ra, dec)])
186 if min_rad > 0 and len(pixels) > 0:
187 vec0 = convert_spherical(ra, dec)
188 min_rad2 = min_rad**2
189 vecs = convert_spherical_array(toRaDec(nside, pixels))
190 dsq = np.sum((vecs - vec0)**2, axis=1)
191 match = dsq > min_rad2
192 pixels = pixels[match]
194 return pixels