Lab05.cpp

#include <Rcpp.h>

using namespace Rcpp;

// [[Rcpp::export]]
List ps_match1(const NumericVector & x) {
  
  int n = x.size();
  IntegerVector indices(n);
  NumericVector values(n);
  
  for (int i = 0; i < n; ++i) {
    int best_n = 0;
    double best_dist = std::numeric_limits< double >::max();
    for (int j = 0; j < n; ++j) {
      if(i==j)
        continue;
      double tmp_dist = abs(x[i]-x[j]);
      
      if (tmp_dist < best_dist) {
          best_dist = tmp_dist;
          best_n =j;
      }
    }
      indices[i] = best_n;
      values[i] = x[best_n];

  }

  return List::create(
    _["match_id"] = indices,
    _["match_x"] = values);
  
}


/*** R
ps_matchR <- function(x) {
  
  match_expected <- as.matrix(dist(x))
  diag(match_expected) <- .Machine$integer.max
  indices <- apply(match_expected, 1, which.min)
  
  list(
    match_id = as.integer(unname(indices)),
    match_x  = x[indices]
  )
  
}

set.seed(1231)
ps_matchR(runif(5))
ps_match1(runif(5))

*/