How to draw a Fourier spectra for my txt file data on MatLab?

Question

I have a ground-based magnetic data in txt file taken every second and I want to plot its Fourier Spectra.

And I notice the spectrogram equation on MatLab need this parameters (window, noverlap, nfft, Fs) which I don't know.

And I notice also that I should do the FFT on my data first before plot its spectrogram, but my data is not discrete and FFt for the discrete data, anyone know how I can do this?

Answer 1

data is discrete by definition. spectrogram and fft give different view s of the data.

spectrogram would be appropriate for a STFT short-time Fourier transform, in case you want to look at successive, overlapping windows of time. fft is the method spectrogram will use to compute the transform.

. Fs is the sampling rate, which you say is once per second, so 1 Hz. Here is one way to view the spectrum,

Fs = 1;
X = fft(data);
N = length(data);
freq = (-N/2:N/2 - 1)*Fs/N;
XmagdB = 10*log10(X.*conj(X));
plot(freq, XmagdB)

Good luck!