How to compare 2 matrices?

Question

Before anything else I must say that I've studied Comparing two matrices with eigen but my question is not the same. Suppose I have two eigen matrices A and B, and I want to edit A in following way:

if (A(i,j) > B(i,j)) A(i,j) = A(i,j) otherwise A(i,j) = B(i,j)

I guess it is possible to do it without an explicit for loop. But I am not very proficient with Eigen yet. What whould be the best approach?

Answer 1

It's A.cwiseMax(B).

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

int main()
{
    Eigen::Matrix2i A = Eigen::Matrix2i::Random();
    Eigen::Matrix2i B = Eigen::Matrix2i::Random();

    std::cout << "A =\n" << A << "\nB =\n" << B << "\n";

    A = A.cwiseMax(B);

    std::cout << "max(A,B) =\n" << A << "\n";
}

Output on my machine is

A =
 730547559  607950953
-226810938  640895091
B =
 884005969 -353856438
-649503489  576018668
max(A,B) =
 884005969  607950953
-226810938  640895091