HI confusion in stacking experiments

This is a collection of a few basic tools based on the paper Jones et al. 2016 to estimate the amount of confusion in HI spectral line stacking experiments. The input values of the HI mass function have been updated to used the Jones et al. 2018 values, while the 2 point correlation function is based on Papastergis et al. 2013. This work assumes WMAP9 cosmology, however, if should be noted that no evolution in the HIMF or 2PCF are included.