R devel - Aug 2003 - R package {genetics} function summary.genotype -- H and (PR#3652)

gerard.tromp@sanger.med.wayne.edu wrote:
> Greetings!
> 
> I found a bug in the function summary.genotype (details below). Essentially
> it appears that the original code from David Duffy used af, allele
> frequency, as a proportion but in the genetics package af is allele
> frequency as a count.
> 
> I tried to submit a bug report together with the fix to CRAN (below). I am
> unsure of the success since the bug report does not appear in the list. I
am
> therefore sending it by e-mail.
Please submit bug reports related to contributed packages to the 
maintainer (in this case Gregory Warnes 
<gregory_r_warnes@groton.pfizer.com>), not to r-bugs.

Uwe Ligges

> Sincerely,
> 
> Gerard
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> Gerard Tromp, Ph.D.                             vox: 313-577-8773
> Center for Molecular Medicine and Genetics      fax: 313-577-7736
> Wayne State Univ. Schl. of Medicine
> 540 E. Canfield, Detroit, MI 48201    gtromp@cmb.biosci.wayne.edu
>                                 mailto:tromp@sanger.med.wayne.edu
>                                      http://cmmg.biosci.wayne.edu
> 
> 
> 
> In function summary.genotype:
> Heterozygosity (H) and PIC are computed using af (allele frequency),
> however, af is derived as a frequency count whereas the computation of H
and
> PIC are in terms of frequency as a proportion.
> 
> Using the example data provided (genetics.R) H and PIC return large
negative
> numbers whereas they are bounded 0,1.
> 
> Output from buggy version:
> *************************************************************************
> Marker: MBP2:C-104T (9q35:-104) Type: SNP
> 
> Number persons typed: 100 (100%)
> 
> Allele Frequency: (2 alleles)
>   Count Proportion
> C   137       0.69
> T    63       0.32
> 
> 
> Genotype Frequency:
>     Count Proportion
> C/C    59       0.59
> C/T    19       0.19
> T/T    22       0.22
> 
> Heterozygosity (Hu)  = -22967    <------ Impossible
> Poly. Inf. Content   = -1.5e+08  <------ Impossible
> ***************************************************************************
> 
> Output from fixed version:
> ***************************************************************************
> Marker: MBP2:C-104T (9q35:-104) Type: SNP
> 
> Number persons typed: 100 (100%)
> 
> Allele Frequency: (2 alleles)
>   Count Proportion
> C   137       0.69
> T    63       0.32
> 
> 
> Genotype Frequency:
>     Count Proportion
> C/C    59       0.59
> C/T    19       0.19
> T/T    22       0.22
> 
> Heterozygosity (Hu)  = 0.44     <--- Correct
> Poly. Inf. Content   = 0.34     <--- Correct
> ***************************************************************************
> 
> 
> 
> 
> Fix is detailed below.
> ***************** 2539,2554 c 2539,2565
> ********************************************
>     ### from code submitted by David Duffy <davidD@qimr.edu.au>
>     #
>     n.typed<-sum(gf)
>     correction<-n.typed/max(1,n.typed-1)
> #  Gerard Tromp 20030803
> #  Heterozygosity and PIC reported are incorrect.
> #  Problem due to use of af which is a count rather than prop.table(af) a
> #    proportion (fraction) less than 1. Definition of af changed?
> #
> ##  Original
> #    ehet<-(1-sum(af*af))
> #   the following produces desired result
>     ehet<-(1-sum(prop.table(af)*prop.table(af)))
> ##  Original
> #    matings<- (af %*% t(af))^2
> #   the following produces desired result
>     matings <- (prop.table(af) %*% t(prop.table(af)))^2
>     uninf.mating.freq <- sum(matings)-sum(diag(matings))
>     pic<- ehet - uninf.mating.freq
> 
>     retval$Hu <- correction * ehet
>     retval$pic <- pic
>     retval$n.typed <- n.typed
>     retval$n.total <- length(object)
>     retval$nallele <- nallele(object)
>     #
>     ###
>
****************************************************************************
> ******
> 
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