FFT of a selected number of data points.

I have a waveform as the one attached and I need to perform FFT over a small section of this waveform (like the one highlighted by a rectangle). How can I do that? I don't have any prior experience of working in frequency domain. Any help would be greatly appreciated.

Answer 1

[Sander Hermanussen]

fft(yoursignal(first_sample,second_sample))

I.e., simply select a range of your signal.

[Aqua22]

Is that it? Matlab says fft(x) or fft(x,n) where n refers to n point dft. Nowhere it tells about a range of signal :-(

[Aqua22]

It does not work.

Answer 2

[Adam]

doc fft
doc colon

[Aqua22]

Thanks