On Thu, Mar 26, 2009 at 12:15 PM, Duijvesteijn, Naomi
<naomi.duijveste...@ipg.nl> wrote:
>
> Hi Readers,
>
>
> I have a question.
>
>
> I have a large dataset and want to throw away columns that have the same
> value in the column itself and I want to know which column this was.
>
>
> For example
>
> > x<-data.frame(id=c(1,2,3), snp1=c("A","G",
> "G"),snp2=c("G","G","G"),snp3=c("G","G","A"))
>
> > x
>
> id snp1 snp2 snp3
>
> 1 1 A G G
>
> 2 2 G G G
>
> 3 3 G G A
>
>
> Now I want to know that snp2 in monomorphic (the same value for the column)
> and after I know which column it is I want to take these columns out.
>
>
> Thanks,
>
> Naomi
>
Another, perhaps slightly more intuitive solution than Jim's would be
the following:
x<-data.frame(id=c(1,2,3), snp1=c("A","G",
"G"),snp2=c("G","G","G"),snp3=c("G","G","A"))
is.monovalued<-function(df){
sapply(df,function(x){
length(unique(x))==1
})
}
monovaluedCols<-is.monovalued(x)
which(monovaluedCols)
x[!monovaluedCols]
/Gustaf
--
Gustaf Rydevik, M.Sci.
tel: +46(0)703 051 451
address:Essingetorget 40,112 66 Stockholm, SE
skype:gustaf_rydevik
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