[R] generic handling of NA and NaN and NULL

[Spencer Graves]

How about:

 > f3 <- function(n){
+   n.pi <- (abs(n)<pi)
+   n.pi[is.na(n.pi)] <- F
+   n.pi
+ }
 >
 > f3(c(1, 5, NA))
[1]  TRUE FALSE FALSE
 >

Spencer Graves

Robin Hankin wrote:
> Hello everybody
> 
> 
> I have a generic problem which the following toy function illustrates:
> 
> f <- function(n) {
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
>                    
> I want it to return TRUE if abs(n)<pi and FALSE otherwise.  f() is
> fine as far as it goes, but does not deal well with NA or NaN or NULL
> (I want these to signal some problem with the argument (ie return
> FALSE), but not to stop execution of f().  In particular, I want f()
> to pass R CMD check )-:
> 
> R> f(NA)
> Error in if (abs(n) < pi) { : missing value where logical needed
> 
> R> f(NULL)
> Error in abs(n) : non-numeric argument to function
> 
> 
> So, how best to patch f() up?  The best I could come up with was:
> 
> f2 <- function(n) {
>   if(is.null(n)){return(FALSE)}
>   if(is.na(n)){return(FALSE)}
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
> 
> This can't be the best way!  Anyway, f2() isn't right: f2(numeric(0))
> fails; note that
> 
> R> if(is.na(numeric(0))){print("asdf")}
> 
> falls over.  help.search("trap") was not very helpful.  try() doesn't
> help either:
> 
> R> try(if(1==NA){print("asdf")})
> Error in if (1 == NA) { : missing value where logical needed
> 
> 
> 
> QUESTION: how to make f() not give an error under any circumstances?
> 
> 
> 
> 
> 
>