Error in the first correlation value obtained using Corrfunc about corrfunc

[lgarrison]

I think this is probably a case of self-counts being included in bins that have a minimum separation of 0 (which is the expected behavior although a little surprising sometimes). It's there to ensure that auto- and cross-correlations yield the same answer. For your case, I think you probably want to subtract off the self-count in the first bin; that is, subtract N from DDtheta.

[ub2206]

Thanks a lot for the response and sorry for the late reply from my side. I would just like to confirm just one thing (in case if I am doing anything wrong).

The N is supposed to be subtracted from the npairs of the auto-correlation term only, am I right? The cross-correlation term should be left as it is.

[lgarrison]

That's right, it won't make a difference for cross-correlations. You may also need to subtract it from the RR term if that's computed with pair counts.

[ub2206]

Thanks a lot for the solutions. The results are much more accurate and explainable now.

[manodeep]

Thanks @lgarrison!

@ub2206 While your issue itself is resolved, since you are effectively computing angular correlation functions over half the sky - it might be worthwhile to check if the runtime improves if you set both link_in_ra and link_in_dec to False.