Check BIC via RcppArmadillo(Rcpp) - rcpp

Question

I want check the BIC usage in statistics.
My little example, which is saved as check_bic.cpp, is presented as follows:
#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]
using namespace Rcpp;
using namespace arma;
// [[Rcpp::export]]
List check_bic(const int N = 10, const int p = 20, const double seed=0){
arma_rng::set_seed(seed); // for reproducibility
arma::mat Beta = randu(p,N); //randu/randn:random values(uniform and normal distributions)
arma::vec Bic = randu(N);
uvec ii = find(Bic == min(Bic)); // may be just one or several elements
int id = ii(ii.n_elem); // fetch the last one element
vec behat = Beta.col(id); // fetch the id column of matrix Beta
List ret;
ret["Bic"] = Bic;
ret["ii"] = ii;
ret["id"] = id;
ret["Beta"] = Beta;
ret["behat"] = behat;
return ret;
}
Then I compile check_bic.cpp in R by
library(Rcpp)
library(RcppArmadillo);
sourceCpp("check_bic.cpp")
and the compilation can pass successfully.
However, when I ran
check_bic(10,20,0)
in R, it shows errors as
error: Mat::operator(): index out of bounds
Error in check_bic(10, 20, 0) : Mat::operator(): index out of bounds
I check the .cpp code line by line, and guess the problems probably
happen at
uvec ii = find(Bic == min(Bic)); // may be just one or several elements
int id = ii(ii.n_elem); // fetch the last one element
since if uvec ii only has one element, then ii.n_elem may be NaN or something
else in Rcpp (while it's ok in Matlab), while I dont konw how to
deal with case. Any help?