I have an R code with a bunch of user-defined R functions. I'm trying to make the code run faster and of course the best option is to use Rcpp. My code involves functions that call each other. Therefore, If I write some functions in C++, I should be able to call and to run some of my R functions in my c++ code. In a simple example consider the code below in R:
mySum <- function(x, y){
return(2*x + 3*y)
}
x <<- 1
y <<- 1
Now consider the C++ code in which I'm trying to access the function above:
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
int mySuminC(){
Environment myEnv = Environment::global_env();
Function mySum = myEnv["mySum"];
int x = myEnv["x"];
int y = myEnv["y"];
return wrap(mySum(Rcpp::Named("x", x), Rcpp::Named("y", y)));
}
When I source the file in R with the inline function sourceCpp(), I get the error:
"invalid conversion from 'SEXPREC*' to int
Could anyone help me on debugging the code? Is my code efficient? Can it be summarized? Is there any better idea to use mySum function than what I did in my code?
Thanks very much for your help.
You declare that the function should return an int
, but use wrap
which indicates the object returned should be a SEXP
. Moreover, calling an R function from Rcpp
(through Function
) also returns a SEXP
.
You want something like:
#include <Rcpp.h>
using namespace Rcpp;
// [[Rcpp::export]]
SEXP mySuminC(){
Environment myEnv = Environment::global_env();
Function mySum = myEnv["mySum"];
int x = myEnv["x"];
int y = myEnv["y"];
return mySum(Rcpp::Named("x", x), Rcpp::Named("y", y));
}
(or, leave function return as int
and use as<int>
in place of wrap
).
That said, this is kind of non-idiomatic Rcpp
code. Remember that calling R functions from C++ is still going to be slow.
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