Looking through the code, it looks like the freqresp function, which is in the lti module, gets imported correctly in the matlab module. (Am not at my computer so haven’t tested this yet). The sys.freqresp method, on the other hand, is deprecated in favor ofsys.frequency_response. So I think the problem might only be that it returns the results in the wrong form (mag and phase rather than complex).

Agh. I must have been looking at some different version. I think the problem is not that the function is missing, but that it is inconsistent with MATLAB. Re-editing title and description. Sorry for the confusion.

Hi, I update the control to version 0.9.0. LTI system can be callable. But I want to caculate the freqresp of a FRD system to get the complex frequency response. If there any solution?

Use H(omega*1j) or H.eval(omega) where H is an FRD function. If you want to evaluate at frequencies other than those that define the frequency response, you need to create a smooth FRD object (use frd(d, w, smooth=True)).