FRF using Fast Fourier transform

As to plot FRF(output) using FFT we plot cross(xf)/auto(ff) v/s frequency. The to plot the Frequency response of input force what we plot auto(FF) v/d frequency ????

[Mathieu NOE]

hello

so you mean you want to plot the autospectrum of the input, then yes, we plot auto(FF) v/s frequency

- FRF of solely the input is not meaningful

[Shubham]

What does auto(FF) signifies.

[Mathieu NOE]

autospectrum of the input