Suppose I wanted to apply some generic operation a matrix consisting of some subset of its values that are not necessarily contiguous. How can I do this?

One application might be that I have an eigen matrix of positive integers:

Code: Select all

Eigen::Matrix<int, 4, 1> mat;
mat << 4, 1, 2, 8;


And I wanted to find the minimum of the 0th, 2nd and 3rd values. If they were contiguous (0th, 1st and 2nd) I could simply call _min_ on the output of a _block_ operation on this matrix, but what do I do in this case?