[Rcpp-devel] How to call a function from an R package in cpp code

[Dirk Eddelbuettel]

On 11 October 2016 at 15:54, Amina Shahzadi wrote:
| I want to use dgev(x,shape=1,scale=1,location=0,log=FALSE) function of an R
| package "FAdist" in the framework of Rcpp. How can I call that?
| 
| For example for the Poisson distribution which is basic function of R I have
| written the following code.
| 
| #include <Rcpp.h>
| using namespace Rcpp;
| 
| //[[Rcpp::export]]
| 
| NumericVector poiss(NumerixVector x, double lam, int give_log)
| {
|         return R::dpois(x, lam, give_log);
| }

First off, your example makes no sense. You probably want to call Rcpp::dpois
as you work on a _vector_ x. Rcpp::dpois closely corresponds to what you have
in R as dpois() __because we an underlying function we can call to do the
same__.

You have said nothing about how FAdist::dgev() is implemented. The answer
will depend on that, and there is nothing we can say as it is stated.

Not everything you see in any given R package as underlying C++ code.

Dirk

-- 
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