R help - Jul 2007 - Calling C Code from R

Hi R Users,
   
  Thanks in advance.
   
  I am using R-2.5.1 on Windows XP.
   
  I am trying to call C code (testCX1.C) from R. testCX1.c calls another C code
(funcC1.c) and returning a value to testCX1.c. I like to have this value in R.
   
  My steps are below:
   
  1. R CMD SHLIB testCX1.c funcC1.c (at command propmt)
   
  2. It creates testCX1.dll with warning (but testCX1.dll works):
   
  testCX1.c:38: warning: implicit declaration of function 'func'
   
  How to get rid off this error ?
   
  What is the best way to call funcC1.c from testCX1.c?
   
  I have provided the codes below:
   
  Once again thank you very much for the time you have given.
   
  Regards,
   
  Debabrata Midya (Deb)
  Statistician
  NSW Department of Commerce
  Sydney, Australia
   
  testCX1.C
  --------------
   
  /*
 *********************
 testCX1.c
  *********************
*/
  #include <R.h>
#include <Rdefines.h>
#include <Rmath.h>
   
  SEXP testC1(SEXP a)
{
   int i, nr;
   double *xa, *xw, tmp;
   SEXP w;
   
     PROTECT(a = coerceVector(a, REALSXP));
   
   nr = length(a);
     printf( "Length : %d \n", nr);
   
   PROTECT(w = allocVector(REALSXP, 1));
   
   xa = REAL(a);
   xw = REAL(w);
    
   tmp = 0.0;
     for (i = 0; i < nr; i++)
     {
        tmp += xa[i];
     }
     // tmp = 0.0;
   xw[0] = func(xa);
     UNPROTECT(2);
   return(w);
}

   
  funcC1.c
  ------------
   
  /*
 *********************
 funcC1.c
  *********************
*/
   
  #include <R.h>
#include <Rdefines.h>
#include <Rmath.h>
   
  SEXP func(SEXP a)
{
   int i, nr = 3;
   double *xa, *xw, tmp;
   SEXP w;
   
     PROTECT(a = coerceVector(a, REALSXP));
   
   PROTECT(w = allocVector(REALSXP, 1));
   
   xa = REAL(a);
   xw = REAL(w);
    
   tmp = 0.0;
     for (i = 0; i < nr; i++)
     {
        tmp += xa[i] * xa[i];
     }
     xw[0] = tmp;
     UNPROTECT(2);
   return(w);
}

  R script
  -----------
   
  dyn.load("testCX1.dll")
xL <- 1:5
xL <- as.double(as.vector(t(xL)))
  .Call("testC1",xL)

  [1] 55
   
   

       
---------------------------------

	[[alternative HTML version deleted]]

On Wed, Jul 04, 2007 at 04:39:18AM -0700, Deb Midya
wrote:
> Hi R Users,
>    
>   Thanks in advance.
>    
>   I am using R-2.5.1 on Windows XP.
>    
>   I am trying to call C code (testCX1.C) from R. testCX1.c calls another C
code (funcC1.c) and returning a value to testCX1.c. I like to have this value in
R.
>    
>   My steps are below:
>    
>   1. R CMD SHLIB testCX1.c funcC1.c (at command propmt)
>    
>   2. It creates testCX1.dll with warning (but testCX1.dll works):
>    
>   testCX1.c:38: warning: implicit declaration of function 'func'
>    
>   How to get rid off this error ?
By adding the prototype of 'func' to testCX1.c:

SEXP func(SEXP a);

Probably it is simplest to collect all prototypes in a single header file
and include that from all .c files.
>   What is the best way to call funcC1.c from testCX1.c?
See .C and .Call and in particular the 'Writing R Extensions' manual,
5 System and foreign language interfaces.

Gabor

[...]

-- 
Csardi Gabor <csardi at rmki.kfki.hu>    MTA RMKI, ELTE TTK