[R] capturing errors in Sweave

[Berwin A Turlach]

G'day Sundar,

On Mon, 1 Mar 2010 23:46:55 -0800
Sundar Dorai-Raj <sdorairaj at gmail.com> wrote:

> Thanks for the input, but I don't want "try" in the Sweave output. I
> want the output to look just like it does in the console, as if an
> uncaptured error really did occur.

I don't think that you will get around using "try"; and you will have
to work moderately hard to make the output appear as it does on the
console.  Probably somewhere along the lines:

++++++++++++++++++++ Sweave code start ++++++++++++++++++++++++++
<<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))
}
@

<<echo=FALSE>>=
tmp <- try(MySqrt())
@ 
<<eval=FALSE>>=
MySqrt()    
@ 
<<echo=FALSE>>=
  cat(tmp[1])
@ 

<<echo=FALSE>>=
tmp <- try(MySqrt("a"))
@ 
<<eval=FALSE>>=
MySqrt("a")
@ 
<<echo=FALSE>>=
  cat(tmp[1])
@ 

<<echo=FALSE>>=
tmp <- try(MySqrt(-2))
@ 
<<eval=FALSE>>=
MySqrt(-2)  
@ 
<<echo=FALSE>>=
  cat(tmp[1])
@ 

<<>>=
MySqrt(4)
@ 
+++++++++++++++ Sweave code end ++++++++++++++++++++++++++++++++++

Now what I would like to know is how to include easily warning messages
in my Sweave output without having to try whether Jean Lobry's [1] hack
still works. :)

HTH.

Cheers,

	Berwin

[1] https://www.stat.math.ethz.ch/pipermail/r-help/2006-December/121975.html

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