[Rcpp-devel] Calling igraph from within Rcpp

[Dirk Eddelbuettel]

On 15 March 2018 at 16:29, Pavankumar Gurazada wrote:
|  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:

This is a cross-posted (which we discourage) over at StackOverflow at where I
saw it first and already answered it:

https://stackoverflow.com/questions/49299368/calling-igraph-from-within-rcpp

In short, needs these two lines (or equivalent) in the middle:

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

  S4 A_m = get_adjacency(Named("g", g));


Dirk

 
 
| #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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