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Find quasar pairs using KDTree
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| import scipy.spatial | |
| from astropy.table import Table | |
| dat = Table.read('sources_ra_dec_z.fits') | |
| ok = ((dat['z'] > 0) | |
| & (dat['ra'] > 150.0) & (dat['ra'] < 151.0) | |
| & (dat['dec'] > 2.0) & (dat['dec'] < 3.0)) | |
| datok = dat[ok] | |
| # hist(dat['z'][ok], bins=50) | |
| x = np.array([datok['ra'], datok['dec']]).transpose() | |
| kdt = scipy.spatial.KDTree(x) | |
| print 'running query_pairs' | |
| radec_pairs = kdt.query_pairs(dist) | |
| pairs = [] | |
| zs = datok['z'] | |
| for i1, i2 in radec_pairs: | |
| if np.abs(zs[i1] - zs[i2]) < 0.2: | |
| pairs.append((i1, i2)) | |
| print len(pairs) # 104192 |
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Oh nice, I didn't even know about
scipy.spatial.KDTree. Laughing now at all the horrible hacks I've seen various people write to do this kind of search (I knew there were better ways but I didn't know of any specific implementations that were convenient to use in Python).