CODEWITHSUNDEEP
reigenrcpp
Jona
Jona

Reputation: 669

Can I convert Eigen::VectorXi to Eigen::VectorXd?

I am using RcppEigen on R. I would like to take a double vector from R layer:

RcppExport SEXP testfunc (SEXP a) {
    const Eigen::Map<Eigen::VectorXd> vecD(as<Eigen::Map<Eigen::VectorXd> >(a));

But, number is comming as integer, so I need to get it as integer like this :

RcppExport SEXP testfunc (SEXP a) {
    const Eigen::Map<Eigen::VectorXi> vecD(as<Eigen::Map<Eigen::VectorXi> >(a));

So, I need to convert it to the double. Can I convert Eigen::VectorXi to Eigen::VectorXd ?

Upvotes: 0

Views: 1040

Answers (1)

Dirk is no longer here
Dirk is no longer here

Reputation: 368509

Are you sure you are not getting confused calling with integer from R when you meant numeric aka double or vice versa ? There is no reason not to have two functions, or to dispatch inside your function.

Eg consider the code here (using Rcpp 0.10.0 features)

#include <RcppEigen.h>

// [[Rcpp::depends(RcppEigen)]]

// [[Rcpp::export]]
double vecdSum(SEXP x) {
    const Eigen::Map<Eigen::VectorXd> 
       vec(Rcpp::as<Eigen::Map<Eigen::VectorXd> >(x));
    return vec.sum();
}

// [[Rcpp::export]]
int veciSum(SEXP x) {
    const Eigen::Map<Eigen::VectorXi> 
       vec(Rcpp::as<Eigen::Map<Eigen::VectorXi> >(x));
    return vec.sum();
}

which we can easily put to use via

R> sourceCpp('/tmp/vecsums.cpp')    # Rcpp 0.10.0 adds this
R> veciSum(c(1L, 2L, 3L))
[1] 6
R> vecdSum(c(1, 2, 3))
[1] 6
R>

Upvotes: 2

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