[R] Can someone please help me understand this? (Was Re: calling R's optimization routines from C)
Globe Trotter
itsme_410 at yahoo.com
Thu Mar 30 06:10:26 CEST 2006
Dear list,
Can someone please help me here? Is it not possible to use the R library for
optimization and other routines calling from C?
Thank you!!
AarEm Trotter
--- Globe Trotter <itsme_410 at yahoo.com> wrote:
> Hi,
>
> I have read R's Writing Extensions manual and am still confused about how to
> use some of the routines there when I call from C. Specifically, I am writing
> a
> little test function which I will optimize using the nmmin function which
> underlies R's optim() with Nelder-Mead. I guess I wonder what library/header
> files I should be using. I was using R_ext/Applic.h and linking with libR but
> I
> can not get it to work. (Btw, I am using RHEL4/FC4 Linux).
>
> The function is very simple: all it does is calculate the sum of squared
> differences from a parameter, so the minimizer will be the mean.
>
> Actually, here is my code:
>
> #include<stdio.h>
> #include<stdlib.h>
>
> #include <R_ext/Applic.h>
>
> typedef struct {
> double *X;
> int n;
> } MyData;
>
> double myfunc(int m, double *par, void *ex)
> {
> MyData *mydata = ex;
> double *X = mydata->X;
> int n = mydata->n;
> double mu = par[0];
> double sum = 0.0;
> int i;
>
> for (i=0; i<n; i++) {
> double t = X[i] - mu;
> sum += t*t;
> }
> return sum;
> }
>
> int main(void)
> {
> int i,n=1, trace=1, maxit=100, fail, fncount;
> double *par, abstol=0.0001, intol=.0001, alpha=1, beta=.5, gamma=2, *xin,
> *x,
>
> Fmin;
>
> MyData ex;
>
> par=malloc(n*sizeof(double));
> xin=malloc(n*sizeof(double));
> x=malloc(n*sizeof(double));
>
> par[0]=5;
> xin[0]=5;
>
> ex.n=5;
>
> ex.X=malloc(ex.n*sizeof(double));
>
> for(i=0;i<ex.n;i++) ex.X[i]=i;
>
> nmmin(n,xin,x,&Fmin,myfunc,&fail,abstol,intol,&ex,alpha,
> beta,gamma,trace,&fncount,maxit);
> free(par);
> free(x);
> free(xin);
> free(ex.X);
> return 0;
> }
>
>
> I compile using the following:
>
> gcc -o testex testex.c -std=c99 -Wall -pedantic -I/usr/lib/R/include
> -L/usr/lib/R/lib -lm -lR
>
> Which actually compiles without error, but I get Segmentation fault when I
> run
> it.
>
> Clearly, I am doing something wrong. Can someone please provide suggestions?
>
> Many thanks and best wishes,
> Aaarem
>
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