[Rd] unable to load shared object - opencv

niandra gianluca.mastrantonio at yahoo.it
Thu Nov 8 21:19:33 CET 2012

Hi all

i'm trying to use the opencv's function into R.

i wrote a simple script, just for try to understand how use c++ in R, it
loads an image and write it with a different name (i know it ), and then
write "Hello, World". The file is names prova2.cpp (is the first time i try
to use c++ )

#include <stdio.h>
#include <opencv/cv.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv/highgui.h>
#include <opencv/cv.h> 
#include <R.h>
#include <Rinternals.h>

extern "C" SEXP provaR(void) {
cv::Mat gravit;
Rprintf("Hello, World!nn");
return R_NilValue;

Now in the terminal  i type R CMD SHLIB  prova2.cpp to create the file
prova2.so and this happen without error.

In R i type dyn.load("prova2.so") and get this error:

Errore in dyn.load("prova2.so") : 
  unable to load shared object
6): Symbol not found: __ZN2cv11_InputArrayC1ERKNS_3MatE
  Referenced from:
  Expected in: flat namespace
 in /Users/niandra/Desktop/statistico/r/builtpack/ProvaScript/prova2.so

I understand that the problem is because i should tell R where to find the
opencv library, but i really don't know how do it.

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