EEG is a voltage signal in time domain (voltage amplitude vs time). how can we convert this EEG into amplitude vs frequency?

EEG is a voltage signal in time domain (voltage amplitude vs time). how can we convert this EEG into amplitude vs frequency? for getting sub-bands such as alpha, beta, theta, gamma and delta which one is best ? means

• "voltage amplitude vs time" EEG signally is best ? or
• "amplitude vs frequency" EEG signal is best ?.

Answer 1

[Daniel M]

To convert from the time domain to the frequency domain, use the fft function. Though you might actually get more use out of the short time Fourier transform (STFT) using the spectrogram function. This gives you amplitude vs frequency for each time window that you choose. Then you could average the results over the frequency bands of interest.