[R] Error message in ifthen else

[Duncan Murdoch]

On 02/10/2008 10:07 PM, Jason Lee wrote:
> Hi,
> 
> I came across the below error when I try to do ifelse condition:-
> 
> Error in "[<-"(`*tmp*`, test, value = rep(yes, length = length(ans))[test])
> :
>         incompatible types
> 
> What I am trying to accomplish is :-
> 
> for(x in 1:ncol(filterpred)){
> 
> sumno<-sum(filterpred[no,x])
> sumyes<-sum(filterpred[yes,x])
> 
> ifelse(sumno==0 && sumyes !=0,
> filterpred[,x]<-NULL,filterpred[,x]<-filterpred[,x])
> }
> 
> Anything wrong here?

You want to use if .. else .., not ifelse.  ifelse() is a function that 
takes a vector of logical values, and produces a vector of answers, not 
a way to control program flow.

It almost never makes sense to use && in ifelse(), because && always 
produces a scalar, not a vector.  I think what you want is to replace 
the ifelse() call with

if (sumno==0 && sumyes !=0) {
   filterpred[,x]<-NULL
} else {
   filterpred[,x]<-filterpred[,x])
}

Duncan Murdoch