RcppExamples (version 0.1.9)

RcppMatrixExample: Example of using Rcpp NumericMatrix

Description

The NumericMatrix class represents numeric matrices

Details

The C++ code presented in the MatrixExample.cpp file:

        #include <Rcpp.h>
        #include <cmath>
// suncc needs help to disambiguate between sqrt( float ) and sqrt(double) 
        inline static double sqrt_double(double x) { return ::sqrt(x); }
using namespace Rcpp;
// [[Rcpp::export]]
        List MatrixExample(const NumericMatrix & orig) {
            NumericMatrix mat(orig.nrow(), orig.ncol());
// we could query size via
            //   int n = mat.nrow(), k=mat.ncol();
            // and loop over the elements, but using the STL is so much nicer
            // so we use a STL transform() algorithm on each element
            std::transform(orig.begin(), orig.end(), mat.begin(), sqrt_double );
return List::create(Named("result") = mat, 
                                Named("original") = orig);
        }

References

Writing R Extensions, available at https://www.r-project.org.

Examples

# NOT RUN {
M <- matrix((1:16)^2, 4)
RcppMatrixExample(M)

# }