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evotools / hapbin

Efficient program for calculating Extended Haplotype Homozygosity (EHH) and Integrated Haplotype Score (iHS)
GNU General Public License v3.0
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Hapbin standardised iHS values sign issue #55

Closed paolo002 closed 5 years ago

paolo002 commented 5 years ago

Hi Colin

This is Paolo again, I have used the latest version of hapbin and I have compared the values of the standardised iHS obtained by running it with same values obtained after running selscan on a same set of individuals and same chromosome. The standardised values obtained after running hapbin have opposite sign compared to those obtained by selscan. I think there is an issue with that. Still the sign is flipped. Please, can you double check?

prenderj commented 5 years ago

Hi

Selscan swapped the reference and alternative EHH relative to the original Voight paper when calculating iHS. See the lines from the paper:

Note that this definition differs slightly from that in Voight et al. (2006) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4166924/#msu211-B7, where unstandardized iHS is defined with iHH1 and iHH0 swapped.

Cheers James

On Mon, 11 Feb 2019 at 15:19, paolo002 notifications@github.com wrote:

Hi Colin

This is Paolo again, I have used the latest version of hapbin and I have compared the values of the standardised iHS obtained by running it with same values obtained after running selscan on a same set of individuals and same chromosome. The standardised values obtained after running hapbin have opposite sign compared to those obtained by selscan. I think there is an issue with that. Still the sign is flipped. Please, can you double check?

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paolo002 commented 5 years ago

Hi James Thank you very much for your reply. I understand. I double checked the raw data and selscan is calculating the iHS as log(iHH1/iHH0) instead hapbin is calculating it as log(iHH0/iHH1). That is the reason why the sign is flipped. So, just to double confirm with you, because I need be 100% sure about the sign of the iHS values because I need to identify which one of the allele, between the reference allele and the alternate one, is under selection... If Hapbin is calculating iHS as log(iHH0/iHH1) meaning Reference allele over Alternate allele, does it mean that a positive iHS value correspond to selection on Reference allele while a negative iHS value correspond to selection on Alternate allele? Is that correct?

Best Paolo