[R] testing for integer

[Bob Wheeler]

Everything is double. You might try n==floor(n).

Faheem Mitha wrote:
> 
> Dear People,
> 
> Consider the following fragment of R code
> 
> choose <- function(n,r)
> {
>   if( is.integer(n) && is.integer(r) && n > 0 && r >= 0 )
>     {
>       .C("choose",as.double(n),as.double(r),comb = double(1))$comb
>     }
>   else stop("n must be a positive integer and r a non-negative integer.")
> }
> 
> This is a practice function (n choose r), which I wrote using a call to C
> code. Unfortunately, there is the following problem. I thought I would put
> in error checking for whether the arguments were integers. However,
> is.integer(1), for example, returns FALSE. However is.numeric(1) returns
> TRUE. It seems that explicit coercion is required for this ie.
> is.integer(as.integer(1)) returns true However, I can't use as.integer,
> because it is too aggressive for just error checking: it rounds off the
> value to the greatest integer less than. Can anyone suggest a suitable
> method of checking for an integer in this case?
> 
>                                  Sincerely, Faheem Mitha.
> 
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-- 
Bob Wheeler --- (Reply to: bwheeler at echip.com)
        ECHIP, Inc.
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