[FieldTrip] problem with ft_multiplot and planar gradient 

jan-mathijs schoffelen jan.schoffelen at donders.ru.nl
Thu Feb 3 20:29:04 CET 2011

Dear Luisa,

Could you please specify whether this is a new problem that didn't  
occur before? If you didn't have problems before, approximately when  
did it stop working the way you expected it to work?
As to the multiplot problem: To me, it seems as if the y-axis is  
plotted at time point 0, which is indeed far away from your latency of  
interest, which is (surprise) between 0.14 and 0.18 s. This is a  
property of multiplotER, which by default plots the x and y axes.  
Should be possible to switch it off.
As to the topoplot problem: difficult to say without additional info /  
data to reproduce the problem. I assume you have used ft_combineplanar  
first before attempting to plot the planar gradient representation?  
Did everything go well in the previous steps, i.e. proper baseline  
correction etc, prior to timelockanalysis? Be sure also to not use the  
baseline-correction option for the plotting in ft_topoplotER.

Best wishes,


On Feb 3, 2011, at 7:07 PM, Luisa Frei wrote:

> 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
> <Picture 4.png><Picture 3.png>
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Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793

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