Filter frequencies in matlab's spectrogram

I have a huge data from my experiments on which I am performing a short-term fft. For this I use, Matlab's spectrogram. The minimum meaningful frequency that can come out of this analysis is given by Rayleigh frequency (1/window-size).For my analysis I use a window size of 0.05 second. So my meaningful minimum frequency would be 20 Hz.

Now, I'd like to filter 0 to 20 Hz in my spectrogram that matlab produces. How do I do this with spectrogram function?

P.S: I'm a newbie to matlab. So any help from matlab experts would be greatly appreciated.

[Star Strider]

You have to filter before you call spectrogram.

What do you mean by ‘filter 0 to 20 Hz’?

What do you want to do?

[Saravana Kumar R]

@star Strider : I want to filter out frequencies from 0 to 20 Hz and do spectrogram for the remaining frequencies. (I do not mean to change the axis minimum or maximum.)

Answer 1

[Star Strider]

Use a high-pass filter with a 20 Hz cutoff. The filter design (Butterworth, Chebyshev, etc.) depends on the result you want.

There are many ways in MATLAB to design filters. My filter design procedure is here: How to design a lowpass filter for ocean wave data in Matlab?