[Eeglablist] Topoplot - data interpolation

[Stephen Politzer-Ahles]

Hi Mariana,

For topoplot() you need a channel locations structure (this could come from
a locations file function, or from the EEG.chanlocs structure that might
exist after you import your data to EEGLAB). Then you need a <channels>x1
vector of data, where <channels> is the number of channels you had and each
number is a voltage at that channel (it can either be a voltage from a
single sample, or an average over some time window). I've never tried using
topoplot() on a two-dimensional data matrix so I'm not sure what would
happen.

Once you have those two things, topoplot() should be pretty
straightforward. For example, if my vector of data were in a variable
called "avg" and I already had read data into EEGLAB, I would use the
follow code to make a topoplot (of course there are also many other options
you can tweak, see 'help topoplot' for more information):

figure; topoplot( avg, EEG.chanlocs ) % EEG.chanlocs can be replaced with a
location file name, e.g. 'my_loc.xyz'

topoplot() does not interpolate any channels. The 'interpolation' it does
is just interpolating the space in between channels (for the purpose of
coloring in the plot). So it should not be a problem if you've interpolated
channels (if your cap is really a 100-channel cap). If you already
interpolated the space between the channels, then all you should need to do
is go back to the original data (the <channels>x1 vector of data) and feed
that into topoplot() instead.

Best,
Steve


On Thu, Apr 18, 2013 at 1:06 AM, Mariana Branco
<marianapbranco1 at gmail.com>wrote:

> Dear Makoto,
>
> I have already my data interpolated into a 100x100 matrix and my issue is:
> how can I plot is on a Head Plot, similar or equal to the one  Topoplot()
> retrieves?
> I believe topoplot only receives a list of channels and locations and
> interpolates the data. However, I have already interpolated the data, so I
> just need to plot it.
>
> Regards,
> Mariana Branco
>
> On 18 Apr 2013, at 02:56, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>
> Dear Mariana,
>
> Open tools - interpolate electrodes to see if that's what you want. If
> not, please ask your question again with more detail.
>
> Makoto
>
>
> 2013/4/9 Mariana Branco <marianapbranco1 at gmail.com>
>
>> Dear Sir/Madam,
>>
>> I just started working with EEGLab toolbox and I am looking for a
>> plotting function like Topoplot, but that does not interpolate the
>> channels, but receives instead as input a matrix with the interpolated
>> channels. Is there any function or option that allows this? Or is it
>> possible to alter the Topoplot function for this purpose?
>>
>> Thank you for the help,
>> Mariana Branco
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>
>
> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>
>
>
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-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/
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