[R] same value in column-->delete

[Uwe Ligges]

Patrizio Frederic wrote:
> this works
> 
> which.is.not.unique <- apply(x,2,function(x)ifelse(length(unique(x))==1,F,T))
> x[,which.is.not.unique]
>


or you simplify that idea and say

x[, apply(x, 2, function(x) length(unique(x)) > 1)]

Uwe Ligges



> 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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> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.