[R] Matrix variable in C code

[depire@inrets.fr]

Selon Gabor Csardi <csardi at rmki.kfki.hu>:

> On Thu, Feb 02, 2006 at 03:11:42PM +0100, depire at inrets.fr wrote:
> [...]
> > 
> > and my test code in C is:
> > ================================================
> > SEXP VPCEfron(SEXP f, SEXP SR, SEXP ZR, SEXP DIR, SEXP nsR, SEXP rho)
> > {
> > 	int taille=INTEGER(nsR)[0];
> [...]
> > 
> > All works, except ZS, the variable ZS is a matrix in R, and when i try to
> give
> > to C code, with ZR, ZR is only a vector.
> > 
> > How to obtain a matrix variable in C ?
> 
> A matrix is the same as a vector (stored columnwise), except that is has a 
> dim attribute. Use can use SET_DIM to set the dim attribute, and GET_dim to
> query it. Eg:
> 
> int nrow=INTEGER(GET_DIM(ZR))[0];
> int ncol=INTEGER(GET_DIM(ZR))[1];
> 
> To access the values in the matrix you might use something like:
> 
> #define RMATRIX(m,i,j) (REAL(m)[ INTEGER(GET_DIM(m))[0]*(j)+(i) ])
> 
> and then 
> 
> RMATRIX(ZR, 0, 1), etc. works. Note that according to this #define the
> matrix
> is indexed from zero.
> 
> Gabor
> 
> 
> -- 
> Csardi Gabor <csardi at rmki.kfki.hu>    MTA RMKI, ELTE TTK
> 
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> 

I try but i think that i make some mistake because i obtain segment fault.
To be sure, i reduce the code to permit to test it, the goal is just to print
the variable, i try with vector variables (real X and integer dX in the
following), it works; but with matrix it doesn't work.

The code of the R program - Test.R
=====================================
X<-c(4,2,3,2)
Z<-c(40,21,30,20)
dX<-c(2,1,1)

dyn.load("test.so")

Phi<-function(z,a,b)
{
	Phi<-z
}

VPEfron<-function(XType,ZType,dXType,G,c0,c1)
{
	# A OPTIMISER
      VPCEfron<-function(f,XT,ZT,dXT,tailleS=length(XT))
      {
		f.check<-function(x) {
            x<-f(x)
            }
     
.Call("VPCEfron",body(f.check),as.double(XT),as.double(ZT),as.integer(dXT),as.integer(tailleS),new.env())
	}
GG<-function(z) G(z,c0,c1)

Vraisemblancepartielle<-VPCEfron(GG,XType,ZType,dXType)
}

resultat<-VPEfron(X,Z,dX,Phi,0,0)
==============================

The code of C code - test.c and test.so is obtained by "R CMD SHLIB test.c"
================================
#include <R.h>
#include <Rdefines.h>

#define RMATRIX(m,i,j) (REAL(m)[ INTEGER(GET_DIM(m))[0]*(j)+(i) ])

SEXP mkans(double x)
{
	SEXP ans;
	PROTECT(ans = allocVector(REALSXP,1));
	REAL(ans)[0]=x;
	UNPROTECT(1);
	return ans;
}

SEXP VPCEfron(SEXP f, SEXP XR, SEXP ZR, SEXP DIR, SEXP rho)
{
	double* X=REAL(XR);
	int* DI=INTEGER(DIR);
	int nligne=INTEGER(GET_DIM(ZR))[0];
	int ncol=INTEGER(GET_DIM(ZR))[1];

	printf("verifie de X: %f - %f - %f - %f\n",X[0],X[1],X[2],X[3]);
	printf("verifie dX: %d %d %d\n",DI[0],DI[1],DI[2]);
	printf("verifie de Z\n");
	printf("%d %d\n",nligne,ncol);
	printf("%f %f\n",RMATRIX(ZR,0,0));
	printf("%f %f\n",RMATRIX(ZR,0,1));
	printf("%f %f\n",RMATRIX(ZR,1,0));
	printf("%f %f\n",RMATRIX(ZR,2,0));

	return mkans(0.0);
}
=====================================

You can save these two simple programs in order to test my code.

Thanks.