estimate Filter of given input and output signal datas

Hi everyone! I am trying to use etfe for a given datasample: Y = F*U where U and Y are the given datas. The U datas are fourier transformed of a recorded sound corrupted with noise. While Y are the filtered datas.

I am trying to do following step: ge = etfe(F,[],fs); %frequency of sound: fs = 44100 If i try to make a Bodeplot of ge, it tells me ge is in the time domain: [color=red] Warning: A bode plot is not well defined for a time series model. The plot will show the output spectrum of the model. Consider using the "idlti/spectrum" command instead.[/color]

Now I am wondering, how can I tell the command bode this datas are in the frequency domain? Or maybe someone does know a better way to try to estimate the filter?