Jeff Brown wrote: > > Hi, > > I'm trying to learn to use .C, which lets one invoke compiled C code from > within R. To do that, one has to first get the C code into R as a shared > object, which (I think) means first compiling it (with COMPILE or SHLIB) > and then loading it (with dyn.load()). >
I would suggest taking it a step further and building an R package to hold your compiled code. The pros are: * It keeps the R wrapper scripts and other things you will end up creating packaged together with your code. * It handles compilation automagically during installation. * It handles loading the dylib for you. The only con I can think of is: * It takes ~2 extra minutes of your time to set up. But compared to other languages I have used this is a ridiculously small price to pay for the portability and organization offered by packages. I wrote a post that goes through step-by-step how to do this for the .Call() interface, including example code. You can find it at: http://n4.nabble.com/Writing-own-simulation-function-in-C-td1580190.html#a1580423 In "Writing R Extensions", p. 79, they give the following example of a C program for convolution of two vectors. (The details aren't important; it's just a function that does something to some stuff.) void convolve (double *a, int *na, double *b, int *nb, double *ab) { int i, j, nab = *na + *nb - 1; for(i = 0; i < nab; i++) ab[i] = 0.0; for(i = 0; i < *na; i++) for(j = 0; j < *nb; j++) ab[i + j] += a[i] * b[j] } Jeff Brown wrote: > > The document suggests calling it from R like this (again the details > aren't important): > > conv <- function(a, b) > .C("convolve", > as.double(a), > as.integer(length(a)), > as.double(b), > as.integer(length(b)), > ab = double(length(a) + length(b) - 1))$ab > > I wrote a file, "convolve.c", with nothing but the above C code in it. I > can't figure out how to compile it. I don't understand the syntax (no > parentheses?) and I always get the same information-free error message: > >> list.files() > [1] "AER" "convolve.c" "sendmailR" >> R CMD SHLIB "compile.c" > Error: syntax error >> COMPILE "compile.c" > Error: syntax error >> R CMD SHLIB "compile" > Error: syntax error >> COMPILE "compile" > Error: syntax error >> R CMD SHLIB compile.c > Error: syntax error >> COMPILE compile.c > Error: syntax error >> R CMD SHLIB compile > Error: syntax error >> COMPILE compile > Error: syntax error > > I'm using an Intel MacBook Pro running Leopard. At a console, typing "gcc > --version" yields 4.2.1. I know I'm supposed to be using version 4.2; I > thought 4.2.1 would qualify, but please let me know if I'm wrong about > that. > > For guidance I've been relying on "Writing R Extensions", "R Installatino > and Administration", the "R for Mac OS X Developer's Page", and the > built-in help. Please let me know if there are other important resources > I've missed. > > Many thanks, > Jeff > All R CMD commands must be executed at the command line- i.e. in a Windows CMD shell or Unix/Linux bash shell. They are not meant for use inside the R interpreter. Hope this helps! -Charlie ----- Charlie Sharpsteen Undergraduate-- Environmental Resources Engineering Humboldt State University -- View this message in context: http://n4.nabble.com/Getting-started-with-C-tp1837912p1837936.html Sent from the R devel mailing list archive at Nabble.com. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
