R from C — Simplest Possible Helloworld

Question

What is the simplest possible C function for starting the R interpreter, passing in a small expression (eg, 2+2), and getting out the result? I\'m trying to compile with Mi

Answer 1

Here you go. It's the main function, but you should be able to adapt it to a more general purpose function. This example builds an R expression from C calls and also from a C string. You're on your own for the compiling on windows, but I've provided compile steps on linux:

 /* simple.c */
 #include 
 #include 
 #include 
 int
 main(int argc, char *argv[])
 {
    char *localArgs[] = {"R", "--no-save","--silent"};
    SEXP e, tmp, ret;
    ParseStatus status;
    int i;

    Rf_initEmbeddedR(3, localArgs);

    /* EXAMPLE #1 */

    /* Create the R expressions "rnorm(10)" with the R API.*/
    PROTECT(e = allocVector(LANGSXP, 2));
    tmp = findFun(install("rnorm"), R_GlobalEnv);
    SETCAR(e, tmp);
    SETCADR(e, ScalarInteger(10));

    /* Call it, and store the result in ret */
    PROTECT(ret = R_tryEval(e, R_GlobalEnv, NULL));

    /* Print out ret */
    printf("EXAMPLE #1 Output: ");
    for (i=0; i

Compile steps:

$ gcc -I/usr/share/R/include/ -c -ggdb simple.c
$ gcc -o simple simple.o  -L/usr/lib/R/lib -lR
$ LD_LIBRARY_PATH=/usr/lib/R/lib R_HOME=/usr/lib/R ./simple
EXAMPLE #1 Output: 0.164351 -0.052308 -1.102335 -0.924609 -0.649887 0.605908 0.130604 0.243198 -2.489826 1.353731
EXAMPLE #2 Output: -1.532387 -1.126142 -0.330926 0.672688 -1.150783 -0.848974 1.617413 -0.086969 -1.334659 -0.313699