According to Matlab documentation:
sigma plots the singular values of the frequency response of a dynamic system.
bode creates a Bode plot of the frequency response of a dynamic system.
I am reasonably familiar with Bode plots and dynamic systems but I don't understand what the singular values of the system are or how they are calculated. Are they related to the magnitudes of the system (which can be outputted by bode)?
For reference, I have a discrete state-space system which I am attempting to model as a reduced order system. One of the papers I have been using to accomplish this mentions using the sigma function to compare the two models. The paper is 'Dynamic Mode Decomposition with Control' by J.L.Proctor.
Any help with understanding singular values or this sigma function would be appreciated.