fft Value from RAW data

[eeg_chk]

How do we get Alpha fft from raw data e.g. if I use raw_AF7 to get fft of Alpha_AF7 then same will be used to get fft Beta_AF7. This will give same value for Alpha_AF7, Beta_AF7, Theta_AF7, ..... I wish to calculate fft values of all bands

[James]

Here is the FFT code in many different languages: https://rosettacode.org/wiki/Fast_Fourier_transform
An FFT requires a set of values, I would recommend using the last 256 RAW EEG values as a minimum. The number of values you use is called the FFT window. It's quite a complex calculation, so I wouldn't recommend it unless you're good at Math and coding!

[eeg_chk]

Thanks for the guidance.