Why doesn't my state-space model iterate?

I am trying to obtain a State-Space model utilizing the function ssest and having a previous model (sys901_0N) as an initial one. When I run the code, although the number of iterations is set to 100 it only runs through it once, obtaining the same model as the inital one that was set.

How could I overcome this?

ssest = ssest(h,sys901_0N,opt)

[Sam Chak]

You don't have this error?

[João Luís Agostinho Soares Pinto]

h is already defined, it is a set of measurements.

H.H is my y measurement and H.f is my x measurement in frequency

h=idfrd(H.H,H.f,0,'FrequencyUnit','Hz');

Answer 1

[Star Strider]

The iterations are defined inside the function. See the documentation section on Display to see the progress of the estimation.

.

[João Luís Agostinho Soares Pinto]

I have the display option but it appears me "Termination condition: No improvement along the search direction with line search.." and I don't know what could be provoking this

[Star Strider]

The previous system you are using to define the new system cannot be improved upon, at least with respect to the conditions the algorithm uses.

Frequency response (idfrd) estimations are more limited in the available options and results than time-domain (iddata) estimates.