[Eeglablist] how to modify and then save topograph maps?

Markus Gschwind markus.gschwind at gmail.com
Thu Nov 13 10:06:18 PST 2014

Dear Steven,

Thank you very much for your detailed answer. But I fear I still was not

I do not talk about display. I want do modify the topography itself and
SAVE the modified topography in a new one. I want to create artificial
topographies out of existing ones.

So I need to use the XYZ information from EEG.chanloc like in topoplot in
order to know which electrode is right and which left, but I need to
separate it from the topography (which is a simple vector with 204 numbers
according to the 204 electrodes). I would like to modify the values in the
topography in such a way that it appears as a left-right-flipped version,
or any other operation.

So my question is if there is a tool which allows to spatially modify and
SAVE the modified topography, not to modify the display!

Thank you again!
Best, Markus

2014-11-13 3:50 GMT+01:00 Stephen Politzer-Ahles <spa268 at nyu.edu>:

> Hello Markus,
> Regarding your second question: you can type 'help topoplot' to see
> documentation for the topoplot() function (the same goes for any other
> function). In this case, the 'nosedir' parameter allows you to have the
>  nose face in other directions. You can also rotate it an arbitrary amount
> by using the view() command (there's an example in the help documentation)
> or you can do this manually in the Matlab figure by clicking the "Rotate 3D
> button", which looks like a cube. When I tried this it seems like I can
> only rotate around the z-axis; rotating other ways makes the different
> parts of the plot come apart.
> Regarding question (1), if you mean to flip the topography so the nose is
> still at the top but left means right and right means left, I'm not sure if
> there's a built-in way to do that. I was able to do it using this hack, but
> maybe someone else knows a better way:
> 1. Manually rotate the figure around the y-axis; you'll see that the head
> circle, electrode markers, contour lines, etc., all disappear (they are
> being hidden behind the topography itself, which has a lower z-value than
> the rest).
> 2. Get the handles of all the separate parts of the figure using
> list=get(gca,'children').
> 3. In  my case, the 8th handle (list(8)) was the one for the topoplot
> itself. I'm not sure if this is always the case, or if your figures might
> come out different. So anyway, I just set the ZData for this  handle to a
> very high number, which put it "behind" the other parts of the figure
> (contour lines etc.) and made them appear again:  set(list(8),'ZData',
> 5+zeros(size(get(list(8),'ZData'))) ). This made the other parts of the
> plot visible again.
> Hope this helps,
> Steve
> Stephen Politzer-Ahles
> New York University, Abu Dhabi
> Neuroscience of Language Lab
> http://www.nyu.edu/projects/politzer-ahles/
> On Thu, Nov 13, 2014 at 2:45 AM, Markus Gschwind <
> markus.gschwind at gmail.com> wrote:
>> Hi all,
>> Could anyone point me to a way how to modify a given topography (vector
>> with # elements corresponding to EEG.chanloc)
>> 1) so as to flip the topography left-right (I understood it is the y
>> axis?)
>> 2) rotate around a given angle and axis?
>> How can I perform these modifications and the SAVE the new topo-vector in
>> a file?
>> Thanks in advance!
>> Best,
>> Markus
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