modes_system in mdof- example is impossible

[josephcslater]

Unit test case is a wrong answer. There is no such thing as a negative damped or undamped natural frequency.

This is a critical fault.

[josephcslater]

So, here is the issue:
M can never be asymmetric: violation of physics. C and K are only in very special cases. Not for this toolbox. That's very advanced.

This toolbox focuses on purely underdamped systems (overdamped aren't a problem in any reality). So, starting with that, we sort by magnitudes of the eigenvalues, then look at them one complex pair at a time, each pair yields one natural frequency and damping ratio.

I've left the unit test in a failed state as this is something that really needs to get fixed next.