Dear François,
I am conducting Coherence analysis on short epochs (1 second). In the coherence pipeline editor there is the option to set the max frequency resolution and highest frequency of interest. In my case, because of the very short epochs, I am not interested in (and allowed to compute) lower frequency bands. However, there is no option to set the lowest frequency band of interest, and because of this I have to set a higher frequency resolution.
Is there any way to solve this problem? Thanks.
Best,
Arnaud
Hi Arnaud,
This option “Highest frequency resolution” is more a display option than a computation option. The computation of the coherence estimates all the spectrum corresponding to the estimator window (defined by the max frequency resolution - see the option of the PSD in the introduction tutorials, it is presented in a different way but the idea is the same). Therefore, first we obtain all the frequency bins returned by the FFT function.
When the sampling frequency is very high (up to 10kHz in MEG), we obtain coherence values for high frequencies we do not care about. Opening a coherence or power spectrum figure with values up to 3000Hz while interested in values below 100Hz is annoying because it requires 10s of zooming in.
Hence the option to discard everything above a certain frequency.
I don’t think an equivalent is relevant for low frequencies.
Does it make sense?
Ok. Thanks François.
Arnaud