# [Eeglablist] Plotting 3D voltage topography at single time point

Cedric Cannard ccannard at protonmail.com
Wed Mar 3 10:00:55 PST 2021

```Hi,

If you just want to just visualize the topo at different time points, EEGLAB allows you to do that by simply right-clicking the desired time point when looking at your data in pop_eegplot (plot>channel data (scroll)).
That works for both continuous and epoched data.

Cedric

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, March 3, 2021 7:10 AM, Stefon van Noordt <stefonv0 at gmail.com> wrote:

> Dear Kaelasha,
>
> Perhaps not the most elegant solution, but you could manually change the
> data in the EEG structure so that it reflects the voltages at a specific
> time point for each channel. Then you could pass this to the pop_headplot
> function.
>
> % Pull out the voltage values at the time point of interest for each
> channel (where the time point in this example is 1000)
> my_spike_dat = EEG.data(:,1000);
>
> % Load dataset from the same study, then epoch the data to any event (it
> doesn't matter which one as you'll be replacing the data)
>
> % Reduce down to only 2 epochs (as you said, the topo functions typically
> require epoched data)
> EEG = pop_select( EEG,'trial',[1 2] );
>
> % Replace data at each time point with your spike EEG data
> for i = 1:1343;
> EEG.data(:,i,1) = my_spike_dat;
> EEG.data(:,i,2) = my_spike_dat;
> end
>
> % Now you have 2 epochs, were every time point is the same data for each
> channel
>
> % Use pop_headplot to plot 3D map (it doesn't matter which time point you
> choose, so 100 in the example below is arbitrary)
> figure; EEG = pop_headplot(EEG, 1, 100,...
> 'eeg topo', [1 1],...
> 'setup',...
> [0 -24 -48 -0.05 0 -1.57 1080 1140 1110] },...
> 'maplimits',[-1,4],'electrodes','off');
>
> You'll likely want to create your own mesh file and change the values here
> for the transform based on your montage.
>
> Hopefully this will be useful.
>
> Best,
> Stefon
>
> On Tue, Mar 2, 2021 at 7:39 PM Clement Lee cll008 at eng.ucsd.edu wrote:
>
> > Hi Kaelasha,
> > I don't think EEGLAB has a specific function for plotting 3D topographies
> > for data from a single time point. However, the function used to plot the
> > 3D ERP map series is `pop_headplot.m` You may be able to hack it to
> > accomplish what you want.
> > Best,
> > Clement Lee
> > Applications Programmer
> > Swartz Center for Computational Neuroscience
> > Institute for Neural Computation, UC San Diego
> > 858-822-7535
> > On Tue, Mar 2, 2021 at 8:20 AM Kaelasha Tyler kaelasha.tyler at gmail.com
> > wrote:
> >
> > > Hi all,
> > > How do you plot a 3D voltage topography at a single time point in
> > > continuous data?
> > >
> > > I am familiar with plotting 3D topographies with epoched data. Eg:
> > > Plot> ERP map series> In 3D
> > > However in my present case, I am wanting to plot in 3D the voltage
> > > topography at the peak of a single seizure spike and wave. In this case,
> > > there is no epoched data, continuous only. Also, I am not wanting to plot
> > > an average of a whole epoch, but just the time point at the peak of the
> > > spike and wave.
> > > If anyone can help me with this, that would be greatly appreciated.
> > > Regards,
> > > Kaelasha
> > >
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