[R] capturing errors in Sweave

[Sharpie]

Sundar Dorai-Raj-2 wrote:
> 
> Hi,
> 
> I'm writing a manual using Sweave and I want to be able to print errors
> from
> bad code. Here's an example:
> 
> <Function-4a>>=
> MySqrt <- function(x) {
>   if (missing(x)) {
>     stop("'x' is missing with no default")
>   }
>   if (!is.numeric(x)) {
>     stop("'x' should only be numeric")
>   }
>   if (x < 0) {
>     stop("'x' should be non-negative")
>   }
>   return(sqrt(x))
> }
> MySqrt()
> MySqrt("a")
> MySqrt(-2)
> MySqrt(4)
> @
> 
> And I would like the output to be:
> 
> MySqrt <- function(x) {
> ...
> }
>> MySqrt()
> Error in MySqrt() : 'x' is missing with no default
>> MySqrt("a")
> Error in MySqrt("a") : 'x' should only be numeric
>> MySqrt(-2)
> Error in MySqrt(-2) : 'x' should be non-negative
>> MySqrt(2)
> [1] 1.414214
> 
> I.e. I want the Error statements to print in the tex file and not just
> make
> Sweave to bomb.
> 
> Thanks,
> 
> --sundar
> 

You can catch errors in R using the try() function:

  foo <- try( log("A"), silent = TRUE )

  if( class( foo ) == 'try-error' ){

    print( unclass( foo ) )

  }

[1] "Error in log(\"A\") : Non-numeric argument to mathematical function\n"


There might be a more clever way to override the default error handling that
would save you from wrapping everything in try()-- but this method should
work.

Hope it helps!

-Charlie

-----
Charlie Sharpsteen
Undergraduate-- Environmental Resources Engineering
Humboldt State University
-- 
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