Yet another (header-only) C++ implementation of 2D matrices. I like this one because I also have a python module for IO, so it's really easy to go from numpy to C++
To use the C++ header, just include that header. It's self contained (except for some standard headers). It works with C++03 spec (although I would love to use some C++11 tricks in the future).
You can use the save and load methods to persist to disk. If you use the python module, you can use the read_tm and write_tm for IO as well - they will write and read numpy matrices.