[R] same value in column-->delete

[Patrizio Frederic]

this works

which.is.not.unique <- apply(x,2,function(x)ifelse(length(unique(x))==1,F,T))
x[,which.is.not.unique]

patrizio

2009/3/26 Duijvesteijn, Naomi <Naomi.Duijvesteijn at ipg.nl>:
>
>   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
>
>
>
>
>
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