CODEWITHSUNDEEP
c++rrcpprcpp11
Nicolas H
Nicolas H

Reputation: 545

Rcpp maximum value by removing several element

I'm trying to write down the distance function which calculate the maximum distance between each rows of matrix, however, before calculate the maximum value, I need to remove certain element, the question is posted in the code.

How can I accomplish it in an efficient way?

#include <Rcpp.h>
Rcpp::NumericMatrix Mydist (const Rcpp::NumericMatrix & x){
unsigned int ans = x.nrow(), i = 0, j = 0;
double d;
Rcpp::NumericMatrix out(ans,ans);

for (i = 0; i < ans - 1; i++){
Rcpp::NumericVector temp = x.row(i);
for (j = i + 1; j < ans ; j ++){
  #
  # here, I need to remove the i and j element in the vector temp-x.row(j) before I can do 
  # the abs() and max(), but i dont know 
  # how to do it efficiently?
  #
  d = max(abs(temp-x.row(j)));
  #
  out(j,i)=d;
  out(i,j)=d;
}
}
 return out;
}

In R, for the part d = max(abs(temp-x.row(j))); , the equavilent R code I want is

Asuume there is a vector called tem = temp-x.row(j)
d = max(abs(tem[-c(i,j)]))

Upvotes: 0

Views: 173

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