Tajima's D equation - VCFtools

Question

[misterie]

Hi,

Could you explain me how VCFtools calculate Tajima'S D within 100-kb nonoverlapping window?

I found general equation

https://en.wikipedia.org/wiki/Tajima%27s_D

but it is too general. I need equation that can I apply directly to VCF file. Thank you in advance.

[Pierre Lindenbaum]

implementation : https://github.com/vcftools/vcftools/blob/f7aee6d26885064d834199052573e31338240b76/src/cpp/variant_file_output.cpp#L3940