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nnrank.cpp
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nnrank.cpp
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#include <RcppArmadillo.h>
#include <math.h>
#include <iostream>
using namespace Rcpp;
using namespace arma;
//[[Rcpp::plugins(cpp11)]]
//[[Rcpp::depends(RcppArmadillo)]]
/*Rank all data points according to how many neighbourhoods they are in*/
//[[Rcpp::export]]
uvec sigpointsampling(const mat&knng){
int n = knng.n_rows;
int k = knng.n_cols;
uvec nnnums(n,fill::zeros);
for (int i = 0; i<n; i++){
for (int j = 0; j<k; j++){
int m = knng(i,j);
nnnums(m-1) =nnnums(m-1)+1;
}
}
return nnnums;
}
/*Selecting all initial data points using the NN-rank method*/
//[[Rcpp::export]]
uvec initialpointsamp(const mat&knng, const uvec&nnnums, const int &cats){
uvec nnnum_id= sort_index(nnnums,1);
int n = knng.n_rows;
int k = knng.n_cols;
int center_num = 0;
uvec centers(cats,fill::zeros);
centers(0) = nnnum_id(0);
center_num = center_num + 1;
for (int i = 1; i< n; i++){
int temp_id = nnnum_id(i);
int new_c = 1;
for (int j = 0;j< center_num; j++){
for (int l = 0; l<k; l++){
if (knng(centers(j),l) == temp_id){
new_c = 0;
break;
break;
}
}
}
if (new_c == 1){
centers(center_num) = temp_id;
center_num = center_num+1;
}
if (center_num == cats){
break;
}
}
return centers;
}