eigen/doc/examples/Tutorial_ReductionsVisitorsBroadcasting_visitors.cpp

#include <iostream>
#include <Eigen/Dense>

using namespace std;
using namespace Eigen;

int main()
{
  Eigen::MatrixXf m(2,2);
  
  m << 1, 2,
       3, 4;

  //get location of maximum
  MatrixXf::Index maxRow, maxCol;
  float max = m.maxCoeff(&maxRow, &maxCol);

  //get location of minimum
  MatrixXf::Index minRow, minCol;
  float min = m.minCoeff(&minRow, &minCol);

  cout << "Max: " << max <<  ", at: " <<
     maxRow << "," << maxCol << endl;
  cout << "Min: " << min << ", at: " <<
     minRow << "," << minCol << endl;
}