[R] Convert Sweave document to a function

[Martin Morgan]

Hi David --

On 03/20/2011 12:19 PM, David.Epstein wrote:
> I like Sweave, which I consider to be a great contribution. I have just
> written a .Rnw document that comes to about 6 pages of mixed code and
> mathematical explanation. Now I want to turn the R code into a function. My
> R code currently contains statements like N<-1000 and theta<- pi/10. In the
> next version of the document, I want N and theta to be parameters of a
> function, so that they can be easily varied. My explanation of the code is
> still valid, and it seems to me that, if I only knew how to manage the
> trick, I would need to change almost nothing in the latex.
>
> The document contains about 6 different code chunks, and 7 different chunks
> of latex.
>
> I tried putting
> functionname<- function(N,theta) {
> into the first code chunk and
> }
> into the last code chunk, but Sweave said this was poor grammar and rejected
> it.

If I understand what you're after, maybe something like

some text describing block 1
<<block1, eval=FALSE>>=
## R code
cat("theta:", theta, "\n"
@
more text describing block 2
<<block2, eval=FASLE>>=
## more R code
cat("N", N, "\n")
@
These get assembled as
<<func>>=
functioname <- function(N, theta) {
<<block1>>
<<block2>>
N * theta
}
@
and to illustrate their use
<<doit>>=
val = functionname(100, 200)
@


>
> Is there a reasonable way to make my .Rnw source into a function definition?
> I would like maintainability of the code to be a criterion for "reasonable",
> and I would like to keep latex explanations of what the code is doing
> adjacent to the code being explained.
>
> One other point is that I will want to export some of the variables computed
> in the function to outside the function, so that they are not variables
> local to the function body. I mention this only because it may affect the
> solution, if any, to my problem.
>
> Thanks for any help
> David
>
> --
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>
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