[Eeglablist] Fixed FFT analysis window for coherence analysis

Arnaud Delorme arno at sccn.ucsd.edu
Fri Apr 8 16:35:09 PDT 2005


Dear Oga,

>I am just wondering how I can change the length of 
>FFT analysis window for computating coherence. 
>  
>
You may use the 'winsize' parameter of the crossf function to set the 
window size.

>And we know the resolution of frequency bins is
>determined by the length of FFT analysis window.
>Actually running "crossf" automatically determines it
>depending on the length of epoch data. 
>We are now analyzing a data with short length of
>epoch (about 150 ms with sampling rate of 2048 Hz), 
>and want to analyze with about 50 ms (around 128 time points) 
>or 100 ms (128 time points) even without stepping. 
>I would like to know how to fix the 
>FFT analysis winodow and stepping window size 
>within this short length under using crossf function.
>  
>
Use "'winsize', 128". You epochs might be too short though. It is better 
to use longer data epochs because the crossf function will reduce the 
output time range by removing half the window size on both sides.

Arno

-- 

* Arnaud Delorme <http://www.sccn.ucsd.edu/%7Earno>, Ph.D.* , SCCN, 
UCSD, San Diego, USA

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