[FieldTrip] problem with ft_multiplot and planar gradient 

Luisa Frei l.frei at psy.gla.ac.uk
Thu Feb 3 19:07:44 CET 2011


Hi everybody,
I have a problem that impacts several analysis steps and I'm hoping  
someone can point me to the right direction.

I have 13 recording sessions, that I want to average, and then I want  
to compute the planar gradients of the average. I first average the  
sessions with ft_timelockanalysis for each session. Then I use  
ft_timelockgrandaverage to combine the sessions.
Then, just to check the data, I plot the ERFs with ft_multiplotER.  
This is when the first problem arises. The x and y axes of the plots  
are shifted in space somehow (see picture 3.png).
Next, I compute the planar gradients. When I plot the topographies  
for the planar gradient, I get a very strange activation pattern,  
that has nothing to do with the ERF topography (which, btw has no  
obvious flaws) and I also get several warnings when I make the plot  
(Picture4.png).

I also know for a fact that the grand average planar gradient should  
look different, as I computed it once before by hand, and it looked  
much more sensible.

If anyone has ever seen this before and can give me a hint as to  
where to look for the error, I would be very grateful.

Luisa




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