[R] if else in R

[David Winsemius]

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