Eigen matrix library coefficient-wise modulo operation

Question

In one of the functions in the project I am working on, I need to find the remainder of each element of my eigen library matrix when divided by a given number. Here is the Matlab equivalent to what I want to do:

mod(X,num)

where X is the dividend matrix and num is the divisor.

What is the easiest way to achieve this?

Answer 1

You can use a C++11 lambda with unaryExpr:

MatrixXi A(4,4), B;
A.setRandom();
B = A.unaryExpr([](const int x) { return x%2; });

or:

int l = 2;
B = A.unaryExpr([&](const int x) { return x%l; });