I am not entirely sure where the matrix and vector come from or when you need them or how you are using them but presumably you could use LAMMPS python interface to do what you need.
As a beginner, I am trying to go through the steps indicated in LAMMPS Tutorial 1 (https://icme.hpc.msstate.edu/mediawiki/index.php/LAMMPS_Help), by running the given example in Unix. However, I got stacked while running LAMMPS as I got an error message indicating that the file "Al99.eam.alloy" couldn't be opened!!
I would appreciate it very much if any one of you who has had any experience so far in dealing with this issue could let me know what went wrong in the process.