On Nov 19, 2013, at 5:30 PM, Gary Dong wrote:
> Dear R users,
>
> I am a R beginner and I am having trouble in using "If Else" in R. Here is
> an example:
>
> ## create a data frame
>
> a<-c(1,2,3,4)
> b<-c(2,0,5,0)
> ab<-data.frame(cbind(a,b))
>
> ##calculate c, which is the ratio between a and b
>
> if(ab$b>0) {
> ab$c<-ab$a/ab$b
> } else {
> ab$c<-0
> }
>
> here is the error I got:
Consider this alternative:
ab$c <- (ab >0 ) * ab$a/ab$b
Although in general, you will probably use `ifelse`.
?ifelse # different than ?"if"
--
David Winsemius
Alameda, CA, USA
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