[Rcpp-devel] Calling igraph from within Rcpp

[Pavankumar Gurazada]

 As a part of utilizing network data drawn at random before further
processing, I am trying to call a couple of functions from the igraph package
at the beginning of each iteration. The code I use is as follows:



#define ARMA_64BIT_WORD#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]// [[Rcpp::plugins(cpp11)]]
using namespace Rcpp;

using arma::sp_mat;
// [[Rcpp::export]]
sp_mat adj_mat(int n, double p) {

  Environment igraph("package:igraph");
  Function game_er = igraph["erdos.renyi.game"];
  Function get_adjacency = igraph["get.adjacency"];

  List g = game_er(Named("n", n), Named("p", p));

  NumericMatrix A_m = get_adjacency(Named("g", g));

  sp_mat A = as<sp_mat>(A_m);

  return A;}


/*** R
set.seed(20130810)
library(igraph)

adj_mat(100, 0.5)*/



So, while the C++ compiles without warnings, the following error is thrown:

> sourceCpp("Hooking-R-in-cpp.cpp")
> set.seed(20130810)
> library(igraph)
> adj_mat(100, 0.5)
Error in adj_mat(100, 0.5) :
  Not compatible with requested type: [type=S4; target=double].

>From the error it looks like I am passing a S4 class to a double? Where is
the error?
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