eigen/doc/examples/Tutorial_ReductionsVisitorsBroadcasting_colwise.cpp

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

using namespace std;
int main() {
  Eigen::MatrixXf mat(2, 4);
  mat << 1, 2, 6, 9, 3, 1, 7, 2;

  std::cout << "Column's maximum: " << std::endl << mat.colwise().maxCoeff() << std::endl;
}