[R] handling a cancelled file.choose()

[Deepayan Sarkar]

On 6/6/07, Ben Tupper <btupper at bigelow.org> wrote:
> Hello,
>
>
> I have a file reading function that prompts the user with a file dialog
> if a filename is not provided in the argument list.  It is desirable to
> return gracefully if the user selects "Cancel", but file.choose() throws
> an error instead of returning something like a character.
>
>  > file.choose()
> [1] "/Users/ben/ben_idl.pref"
>
>  > file.choose()
> Error in file.choose() : file choice cancelled
>
> I naively planned to use nchar() to test the length, assuming
> cancellation would return a zero-length character. That appears to be
> out of the question. [...]

Not really, errors can be caught and handled. This seems to give the
behaviour you want:

tryCatch(file.choose(), error = function(e) "")

-Deepayan