[Rcpp-devel] using RInside calls in a subroutine?

[Dirk Eddelbuettel]

On 7 December 2010 at 12:00, Eileen Meyer wrote:
| I need to call R functions through a C++ subroutine.  The problem is 
| that, as many have pointed out, you can't call the RInside environment 
| more than once.  

News to me.

What you cannot do is _instantiante more than one RInside object_ because R
itself is single-threaded, non-reentrant and whatever evil thing else we can
imagine.

One R program, one RInside instance. Share it within your program. Not that hard.

| So how do I get my subroutine to "know" about R? 

A global variable?  A variable in passed as reference?  

| Can I pass something along?  I am not really a C++ programmer, so I apologize 
| for my ignorance.  (and THANKS for developing some pretty amazing tools)

We cannot make you a C++ programmer via an email or two.  You need to read up
and practice. 

Did you look at the existing examples in the RInside package?

 
| Here is an example of what doesn't work.
| 
| First, the subroutine:
| 
| #include "r_funcs.h"
| std::vector< double > ks_test(std::vector< double >x, std::vector< 
| double >y, int argc, char *argv[]) {

Why do you need to pass argc and argv into the work function?
| 
|    SEXP ans;
| 
|    R.RInside::assign(x,"x");
|    R.RInside::assign(y, "y");

What is R. -- where is it defined?
 
|    std::string evalstr = " \
|      cat('Running ls()\n'); print(ls());    \
|      ks <- ks.test(x,y);            \
|      ks$p";
| 
|    R.RInside::parseEval(evalstr, ans);
|    RcppVector<double> vec(ans);
|    std::vector<double> v = vec.stlVector();
| 
|    return(v);
| }



| 
| header file:
| 
| #ifndef R_FUNCS_H
| #define R_FUNCS_H
| 
| 
| #include <RInside.h>
| //#include <Rcpp.h>
| 
| std::vector< double > ks_test(std::vector< double >x, std::vector< 
| double >y, int argc, char *argv[]);
| 
| #endif //R_FUNCS_H
| 
| 
| the main file:
| 
| #include <stdio.h>
| #include "r_funcs.h"
| 
| int main(int argc, char *argv[]) {
| 
|    RInside::RInside R(argc,argv);
|    // testing stuff
|    std::vector< double > x(5);
|    std::vector< double > y(5);
|    int i;
|    double var[5] = {1,2.2,3.4,4.33,42.4};
|    for(i=0; i<5; i++) {
|      x[i] = var[i];
|      std::cout << x[i] << std::endl;
|    }
| 
|    double var2[5] = {3.224,4.1,4.22,4,4.4};
|    for(i=0; i<5; i++) {
|      y[i] = var2[i];
|    }
| 
|    // correct function call
|    std::vector< double > v = ks_test(x,y,argc,argv);
| 
|    // output
|    std::cout << "In main_stat_compare, ks p-value is " << v[0] << std::endl;
| 
|    exit(0);
| }
| 
| 
| Of course if I move the RInside declaration into the subroutine, this 
| example works, but I can only call the ks test once. :(


See my questions above.  Your example does not even built (and yes, I went
through the trouble of creating three files and adapting the Makefile from
RInside's own examples/standard/Makefile.

But if we can't even build it we can't comment on it.

Sorry, Dirk
 
 
| 
| 
| 
| 
| 
| 
| -- 
| ----------------------------------------
| Eileen Meyer
| 
| Physics&   Astronomy MS-108
| Rice University
| 6100 Main St. Houston, TX 77005
| www.interfolio.com/portfolio/eileenmeyer
| 
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-- 
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com