C++ y Rcpp

Install clang in you system, required for code autocompletion:

  sudo pacman -S clang

Distancia "cruzada"

Referencias:

• https://www.r-bloggers.com/2019/09/matrix-cross-distances-using-rcpp/
• https://support.rstudio.com/hc/en-us/articles/200486088-Using-Rcpp-with-the-RStudio-IDE

Click para mostrar el código de la función: ++++ cross_dist.cpp |

#include <Rcpp.h>
using namespace Rcpp;

// [[Rcpp::export]]
NumericMatrix crossdist(NumericMatrix m1, NumericMatrix m2) {
  int nrow1 = m1.nrow();
  int nrow2 = m2.nrow();
  int ncol = m1.ncol();

  if (ncol != m2.ncol()) {
    throw std::runtime_error("Incompatible number of dimensions");
  }

  NumericMatrix out(nrow1, nrow2);

  for (int r1 = 0; r1 < nrow1; r1++) {
    for (int r2 = 0; r2 < nrow2; r2++) {
      double total = 0;
      for (int c12 = 0; c12 < ncol; c12++) {
        total += pow(m1(r1, c12) - m2(r2, c12), 2);
      }
      out(r1, r2) = sqrt(total);
    }
  }
  return out;
}

++++

Para usar, sourcear el archivo cpp y pasarle las dos matrices en R:

Rcpp::sourceCpp("src/cross_dist.cpp")

m <- crossdist(m1, m2)