Impedance calculation from experimental data

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Gisela on 11 Apr 2016
I have some experimental data (V and I) that I want to use to calculate the impedance Z using matlab. So far I've calculated the Fourier transform for both voltage and current and to calculate the impedance I want to determine the ratio between the two of them. This however gives a vector for each frequency and in order to obtain the Nyquist plot I need to use only one of the values of the vector. Yet I don't know which of the values I have to choose.

Star Strider on 11 Apr 2016
I do not understand what your data are. Do you have a vector or matrix?
Ideally, you would either have the voltage and current measured at each frequency, or the impulse response of which you took the fft. Impedance Z(jω) is by definition a complex quantity, so you would simply calculate Z=V./I to get the complex impedance.
Ruben Díaz Granero on 13 May 2021
Hi! Have you solved your problem? I've exactly the same problem. An Input current data with a voltage response from a modeling circuit. I(t) --> H(s) --> V(t). The teorical solution is applying the FFT to each temporal sine wave and you will obtain I(w) and V(w). Then the ratio V(w)/I(w) it is supposed to be the impedance Z(jw) but I can't reach this point.