Random C++ Part 1: Building a block sparse matrix in Eigen

Code availability The code from this post can be found in my github repo . I’ll be honest with y’all. I was writing something else. It was really long and was getting annoying to edit and was probably never going to be finished. So instead of doing that, I am just going to post this. It’s about making a block matrix in a Stan-compatible way. Why?? Because I wanted to be able to do this. There is…