[R] Odd behaviour of identical()

[R. Michael Weylandt]

I believe it's coming down to the difference between integers and
doubles (the computer data types, not the math-y meaning of those
terms) -- e.g.,

identical( c(0L, 0L), c(0,0) )

Note that sequences made by `:` provide integers when possible: is.integer(1:5)

You may want to use all.equal() instead.

Best,
Michael

On Tue, May 15, 2012 at 11:45 AM, math_daddy <math_daddy at hotmail.com> wrote:
> Consider the following code:
>
> test <- function(n)
> {
>  for(x in 1:n)
>  {
>    for(y in 1:n)
>    {
>      for(r in max(x-1,1):min(x+1,n))
>      {
>        for(s in max(y-1,1):min(y+1,n))
>        {
>          vec <- c(x-r,y-s)
>          print(c("vec = ", vec))
>          print(identical(vec,c(0,0)))
>        }
>      }
>    }
>  }
> }
>
> If you run test(2) you'll see a printout of the values of the vector vec
> followed by a logical telling you whether vec is identical to c(0,0), which
> it will be for certain iterations of the nested loop. However, the logical
> is always FALSE. If I don't perform the loop but instead assign the values
> directly to vec, this problem does not arise. Can anyone tell me what is
> happening here?
>
> Thank you very much in advance for any help.
>
>
> --
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