CODEWITHSUNDEEP
rrcpp
Luca Scrucca
Luca Scrucca

Reputation: 96

Rcpp call an R function with a list of arguments

I would like to call from a C++ function defined using Rcpp and R function by passing a list of arguments, in a way similar to using do.call in R. Here is a silly example:

Suppose I have a vector and I want to compute a trimmed mean. Two possible ways are

x = rnorm(100)
mean(x, trim = 0.1)
do.call("mean", list(x = x, trim = 0.1))

In my specific case using do.call is preferable because it could be a list of several parameters to be used by the function to be called.

Based on some examples found in stackoverflow, I tried to implement the above in C++ as follows:

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
double foo(Function f, List args)
{
    double out = as<double>(f(args));
    return out;
}

The above code does not work if args is a list, but only if is a vector of values.

Any help would be appreciated.

LS

Upvotes: 3

Views: 785

Answers (1)

Qiang Kou
Qiang Kou

Reputation: 522

I am not very sure if the below is what you expect.

#include <Rcpp.h>

using namespace Rcpp;

// [[Rcpp::export]]
double foo (Function f, NumericVector x) {
  double out = Rcpp::as<double>(f(x, Named("trim", 0.1)));
  return out;
}

/*
> x = rnorm(100)
> do.call("mean", list(x = x, trim = 0.1))
[1] 0.1832635
> Rcpp::sourceCpp("test.cpp")
> foo(mean, x)
[1] 0.1832635
*/

Upvotes: 1

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