R help - Feb 2006 - Matrix variable in C code

Dear all,
I try to compute some piece of my R code in C.

My problem is about matrix.

My code in R is the following:
============================================VPEfron<-function(XType,ZType,dX,G,c0,c1)
{
	XS<-sort(XType)
	rang<-sort.list(XType)

     	ZS<-matrix(0,k,max(dX))
	ZS<-ZType[rang,]
	S<-rep(0,length(XType))
	for(i in 1:length(XType))
		S[i]<-sum(ZS[i,])

      VPCEfron<-function(f,S,ZS,dX,tailleS=length(XType))
      {
		f.check<-function(x) {
            x<-f(x)
            }
     
.Call("VPCEfron",body(f.check),as.double(S),as.double(ZS),as.integer(dX),as.integer(tailleS),new.env())
	}
GG<-function(z) G(z,c0,c1)

Vraisemblancepartielle<-VPCEfron(GG,S,ZS,dX)
}
============================================
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];
	int* DI=INTEGER(DIR);
	double* S=REAL(SR);
	double* Z=(ZR);

// just to check the value
	printf("verifie de S: %f - %f - %f\n",S[0],S[1],S[2]);
	printf("verifie dX: %d %d %d\n",DI[0],DI[1],DI[2]);
	printf("verifie k: %d\n",taille);
	printf("verifie de Z\n");
	printf("%f %f\n",Z[0][0]);
	printf("%f %f\n",Z[1][1]);
	printf("%f %f\n",Z[2][1]);
	somme=0.0;
	printf("STOP\n");
return(somme);
}
========================================

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 ?

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