I can't find the algorithm used in fitfrd or fitsys commands, any help is appreciated.

Hi,

Can anyone help me with the algorithm that has been used in fitfrd (used to be fitsys in the previous MATLAB versions)? I know that the command is used to fit the frequency response data with a state space representation model. I want to know the algorithm that is used in these two commands. The MATLAB help document didn't help.

Thanks,

[Joshua Jones]

I came across this answer at a site called Researchgate that refers to a specific page of a specific DSP book from 1975. I have borrowed a copy of the exact edition of this exact book and it says nothing about anything akin to algorithms for fitting (time continuous?) transfer functions at all, certainly not on page 513. Please, if anyone can be of help, I would be much obliged.