[R] C code and R

[Thomas Lumley]

On Mon, 9 Jul 2001, Agustin Lobo wrote:

>
> A couple of questions on calling C programs
> from R functions:
>
> 1. Is there any other guide on this matter in addition to
> Writing R Extensions ?

Not specifically on R. You may find the book "S Programming" by Venables &
Ripley useful.

> 2. Writing R Extensions starts dealing with C programs
> assuming that those have already been compiled:
> "Interface functions .C and .Fortran
>
> These two functions provide a standard interface to compiled code that has
> been linked into R,... "
>
> Are there any constraints that should be considered
> at compiling a function that is intended to be called by R?

Not really, if .C is being used to call it. It is a good idea to use R's
facilities if you want to print to the screen from C code, and it may well
help to use R's memory management (eg Calloc or R_alloc) rather than
managing memory yourself, but these are optional.

While you need to learn more initially it is often more effective to use
the .Call() interface unless you need portability between S and R (and
sometimes even then).

> Splus (unix v 3.x) used to have an script
> (Splus COMPILE) to make sure that the compilation was done
> with the proper flags. Is there an equivalent R COMPILE
> script?

Section 4.4 of "Writing R Extensions" describes how you do this.

	-thomas

Thomas Lumley			Asst. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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