Computing Coherence of Two Signals

lagidigulagidigu
in Research
Hey there!

I've been looking into the math of coherence of signals, and I'm not quite sure how to compute it... Is there a phase variable in the Processing code, or even a coherence one? And in case there isn't, does anyone know any pointers as to how I can compute it? 

Any help would really be appreciated...

Cheers 
Luc :D

Comments

  • lagidigulagidigu
    I should phrase it differently: 

    I've looked throught all the processing code, everything I could find seemed to be the FFT, so we have the Complex Discrete Fourier Transform. Is that sufficient for getting the coherence of two channels?
  • wjcroftwjcroft Mount Shasta, CA
    Related thread over on NeuroBB,


  • lagidigulagidigu
    Thanks a lot for the link!

    What helped me in the end was the following paper:


    I managed to compute the coherence of 2 FFTs in Processing, so it's in real time. If anyone is interested in the code, just PM me, or I can post it! :D

    Cheers
    Luc
  • wjcroftwjcroft Mount Shasta, CA
    Luc, that's great, thanks.

    Do you have a Github link? Or consider posting on Github.

    William

  • lagidigulagidigu
    Sure, you can find it here:


    I am not sure whether or not I have computed it well though. The values are between 0 and 1, of course, but I have noticed the following:

    When measuring frontal alpha (8-12hz) coherence in an eyes closed sample session, the values are dancing around at about .8, which is way too high it seems, doesn't it? When I compare a sample eyes-closed session with a meditation session, my alpha coherence drops.

    Will do some more measurements, but I would be really thankful if someone could look over the code in order to see if there is an obvious mistake... But I'm pretty sure it's right :/

    Cheers

    Luc
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