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Useful snippets for computing correlation functions
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#!/usr/bin/env python | |
import sys | |
import pdb | |
import numpy as np | |
import math | |
try: | |
from esutil import coords | |
import esutil | |
except: | |
print "You need to install esutils!" | |
sys.exit(1) | |
def count_pairs(ra1, dec1, ra2, dec2, theta_bins): | |
"""Fast pair counting routine. | |
Arguments: | |
ra1: RA of first sample, in degrees | |
dec1: DEC of first sample, in degrees | |
ra2: RA of second sample, in degrees | |
dec2: DEC of second sample, in degrees | |
theta_bins: np.array of theta bins | |
Returns: | |
pairs: Pair counts | |
r1: Left side bin edges | |
r2: Right side bin edges | |
""" | |
depth = 10 | |
h = esutil.htm.HTM(depth) | |
ntheta = len(theta_bins) | |
r1, r2, pairs = h.bincount( | |
min(theta_bins), max(theta_bins), ntheta, ra1, dec1, | |
ra2, dec2) | |
print 'Pair results: ', pairs | |
return pairs, r1, r2 | |
def define_random(spec, photo, nrand): | |
"""Generates a random catalog in the same range as an input catalog. | |
Arguments: | |
spec, photo: np.recarrays of spectroscopic and photometric catalogs | |
nrand: integer that is the desired number of random points | |
Output: | |
rand: random catalog (recarray with 'RA' and 'DEC') | |
""" | |
ra_min = np.min(np.array(np.min(spec['RA']), np.min(photo['RA']))) | |
ra_max = np.max(np.array(np.max(spec['RA']), np.max(photo['RA']))) | |
dec_min = np.min(np.array(np.min(spec['DEC']), np.min(photo['DEC']))) | |
dec_max = np.max(np.array(np.max(spec['DEC']), np.max(photo['DEC']))) | |
print '[+] Making a random catalog' | |
rarand, decrand = coords.randsphere( | |
nrand, ra_range=[ra_min, ra_max], | |
dec_range=[dec_min, dec_max], system='eq') | |
rand = np.recarray((nrand,), dtype=[('RA', float), ('DEC', float)]) | |
rand['RA'] = rarand | |
rand['DEC'] = decrand | |
return rand |
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