[Rcpp-devel] Calling igraph from within Rcpp

[Pavankumar Gurazada]

Yes, apologies for getting too eager! I should have waited.

On Thursday, March 15, 2018, Dirk Eddelbuettel <edd at debian.org> wrote:

>
> 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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>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org
>
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