C++ Armadillo: Get the ranks of the elements in a vector

Question

Suppose I have a vector, and I want to get the ranks of the elements if they were sorted.

So if I have the vector:

0.5
1.5
3.5
0.1

and I need returned the ranks of each element:

2
3
4
1

Is there a way to do this in Armadillo? This is different than the previous post since we are getting the ranks and not the indices before sorting.

Answer 1

Here, check this out:

#include<iostream>
#include<vector> // std:: vector
#include <algorithm> // std::sort
#include <map> // std::map

using namespace std;


int main() {
    vector<double> myVector = { 0.5, 1.5, 3.5, 0.1 };
    vector<double> Sorted = myVector;

    std::sort(Sorted.begin(), Sorted.end());

    map<double, int> myMap;

    for (int i = 0; i < Sorted.size() ; i++)
    {
        myMap.insert(make_pair(Sorted[i],i));
    }

    for (int i = 0; i < myVector.size() ; i++)
    {
        auto it = myMap.find(myVector[i]);
        cout << it->second + 1 << endl;
    }

    return 0;
};

Output: