[Eeglablist] Topoplot - data interpolation

[Mariana Branco]

Hi Steve,

The reason why I was questioning about this is because the interpolated data that I have is no longer EEG signal but some features which were applied to the interpolated image that topoplot returns. So, having already a matrix, it would be a loss of information giving back only some point values to the topoplot plot. In fact, some points of my matrix have relevant information that are not located above the channels but in between. These features would be lost if I used topoplot.

Thank you all,
Mariana 

On 18 Apr 2013, at 21:09, Stephen Politzer-Ahles <politzerahless at gmail.com> wrote:

> 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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