Directly Computing \(\xi(r)\) and \(wp(rp)\)ΒΆ
For a periodic cosmological box, the 3-d auto correlation, \(\xi(r)\), and
the projected auto correlation function, \(wp(rp)\), can be directly computed
using the Natural Estimator. The relevant python wrappers are present in
Corrfunc.theory.xi and Corrfunc.theory.wp. See Notes on the Random-Random Term in Autocorrelations
for details on how the Natural Estimator is computed.
>>> import numpy as np
>>> from Corrfunc.theory.wp import wp
>>> from Corrfunc.theory.xi import xi
>>> from Corrfunc.io import read_catalog
>>> X, Y, Z = read_catalog()
>>> boxsize = 420.0
>>> nthreads = 2
>>> pimax = 40.0
>>> nbins = 10
>>> bins = np.linspace(0.1, 10.0, nbins + 1) # Note the + 1 to nbins
>>> wp_counts = wp(boxsize, pimax, nthreads, bins, X, Y, Z)
>>> xi_counts = xi(boxsize, nthreads, bins, X, Y, Z)
See the complete reference here Corrfunc.