Re: [Rd] Sweave tokens not in column 1: enhancement request

From: Friedrich Leisch <Friedrich.Leisch_at_boku.ac.at>
Date: Wed, 20 Apr 2011 12:42:17 +0200

>>>>> On Tue, 19 Apr 2011 13:59:44 -0700 (PDT), >>>>> David Epstein (DE) wrote:

> When I re-use a code chunk in Sweave, together with keep.source=TRUE, I would
> like to follow usual programming conventions in which the amount of white
> space on the left indicates logical structure. It seems that one can't do
> this in Sweave, or am I wrong?

> for (i in ind) {
> do such-and-such and then
> <<code chunk 20>>
> do something-else
> }

> Sweave will say that << is an error. Would it be difficult to change Sweave
> so that formatting in the conventional way becomes possible? I'm thinking
> both of the .Rnw file and of the final output in the .pdf or .ps file.

Not difficult at all, that's a trivial change:

  MySyntax <- utils::SweaveSyntaxNoweb
  MySyntax$coderef <- "^[[:space:]]*<<(.*)>>.*"   Sweave("test.Rnw", syntax=MySyntax)

should do what you want. That code references need to start in column 1 is inherited from noweb, not sure if we really need it. Cannot think of a situation where the above regular expression appears in valid R code, but perhaps I am overlooking something.

Best,
Fritz



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