[R] Rcpp, dyn.load and C++ problems

[Eric Berger]

.Call("compute_values_cpp")
Also, if you were passing arguments to the C++ function you would need to
declare the function differently.
Do a search on "Rcpp calling C++ functions from R"

HTH,
Eric


On Sun, Dec 3, 2017 at 3:06 AM, Martin Møller Skarbiniks Pedersen <
traxplayer at gmail.com> wrote:

> Hi,
>
>   I have written a small C++ function and compile it.
>   However in R I can't see the function I have defined in C++.
>   I have read some web-pages about Rcpp and C++ but it is a bit confusion
> for me.
>
> Anyway,
>   This is the C++-code:
>
> #include <Rcpp.h>
> using namespace Rcpp;
>
> // [[Rcpp::export]]
> List compute_values_cpp(int totalPoints = 1e5, double angle_increment =
> 0.01, int radius = 400, double grow = 3.64) {
>   double xn = 0.5;
>   double angle = 0.1;
>   double xn_plus_one, yn_plus_one;
>   NumericVector x(totalPoints);
>   NumericVector y(totalPoints);
>
>   for (int i=0; i<totalPoints; i++) {
>     xn_plus_one = xn*cos(angle)*radius;
>     yn_plus_one = xn*sin(angle)*radius;
>     angle += angle_increment;
>     xn = grow*xn*(1-xn);
>     x[i] = xn_plus_one;
>     y[i] = yn_plus_one;
>   }
>   return List::create(Rcpp::Named("x") = x, Rcpp::Named("y") = y);
> }
>
> And I compile it like this:
> PKG_CXXFLAGS=$(Rscript -e 'Rcpp:::CxxFlags()') \
> PKG_LIBS=$(Rscript -e 'Rcpp:::LdFlags()')  \
> R CMD SHLIB logistic_map.cpp
> without problems and I get a logistic_map.so file as expected.
>
> However in R:
> R> dyn.load("logistic_map.so")
> R> compute_values_cpp()
> Error in compute_values_cpp() :
>   could not find function "compute_values_cpp"
>
> Please advise,
>   What piece of the puzzle is missing?
>
> Regards
> Martin M. S. Pedersen
>
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>
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