[Eeglablist] std_envtopo (plotchans and pvaf)

[Ana Navarro Cebrian]

>Currently this is not supported. I see how to do it though.
I would suggest that you exclude clusters of non-interest, or specify the
clusters to use, so that your outermost envelope is consist of only
necessary ones.

Thanks Makoto. This is very helpful. I'd still love to be able to choose
some channels though; My P300 comes along with an effect of an opposite
(negative) signal in the frontal electrodes (I think this happens because I
use the average as a reference), and I believe that choosing just some
centro-parietal electrodes would give me a better estimate. I'll see if I
can try something myself.

>-550.46 should be a number of latency. Where does the line (extending from
the scalp topos) pointing? Isn't it -550.46 ms? If so, you should limit the
latency window to evaluate contribution.

It seems to me that the line is pointing at 559 and what I'm talking about
says "pvaf: 550.46. I had limited the latency anyway (from 200 to 600ms).
Another example is the cluster close to it, which shows "pvaf: -111.61".
This one is also pointing at latency ~559ms.

>No, actually pvaf never sums to 100% if you add up each clusters. That
means, pvaf(Cls1+Cls2) ~= pvaf(Cls1)+pvaf(Cls2). By the way the default
100% is pvaf(Cls1+Cls2+...ClsN) if you have N number of clusters.
The measure pvaf is always superadditive i.e. exceeds 100% if summed
separately.

Here I was talking about the individual pvaf (for each individual cluster)
shown under the cluster topoplot, and not the total pvaf. I'm not sure if
the response is still the same.
For example, for those two clusters that I'm talking about above, with pvaf
-550.46% and -111.61%. Would it be possible to get positive values like
those for individual clusters? i.e. pvaf: 550.46?

Thank you again for your help, Makoto.
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