Add autocorrelation function

[ErikOsinga]

Hey Alec,

Very elegant code that's working very well! Given that the computation of pairs and the bookkeeping etc is already there, it would be nice to also add the computation of the autocorrelation function?

Kindly,
Erik

[AlecThomson]

Hey @ErikOsinga!

Thanks for the suggestion! I'm curious how the autocorrelation is defined in the structure function / source pair context. What would be the functional form of the ACF in this case?

Also, if you already have it implemented somewhere I'm always happy to receive pull requests ;)

[amitseta90]

Hello people, saw this repo after a long time, so replying now.

The autocorrelation function can be computed from the SF using Eq. 3 in https://scixplorer.org/abs/2017ApJ...850....4H/abstract (only the factor 2 in the denominator changes for a higher number of points in the stencil).