# Directly Computing $$\xi(r)$$ and $$wp(rp)$$¶

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

See the complete reference here Corrfunc.