Ploting using easycap64ch-avg

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Mon Jan 26 12:32:10 CET 2009


Hi Ana,

This is what I see.


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It looks reasonable to me. The template layout files in fieldtrip/
template/*.lay that have "avg" in their name were all created by
measuring the channel position on a few subjects' head with the
polhemus tracker and averaging over those. Those measurements are not
ideal, explaining the slight asymmetry.

If you are not happy with this template layout (which I can imagine),
I suggest you go to www.easycap.de, download a figure of the cap you
are using, and use

cfg =[]
cfg.image = 'your_figure.gif'
layout = prepare_layout(cfg);

which will allow you to interactively click on each electrode position
in the figure. You then also have to specify the outline of the head
(including ears and nose) which will be displayed in black lines and
the outline of the part of the head in which you want the interpolated
data to show up (i.e. only the cricle of the head).

best regards,
Robert





On 26 Jan 2009, at 12:07, Ana Carolina wrote:

> Dear FieldTrip users,
>
> I'm trying to plot EEG data using the easycap64ch-avg layout, but
> there seems to be a problem with the coordinate values because when
> I see the plot, the electrodes are not on the correct position. When
> I checked the values of the layout I saw that the values of the two
> first columns are not correct (I think), because if you think in all
> the electrodes that are in the same line like 35, 20, 8, 2, 1, 5,
> 14, 43 and 46 they should have the same value in the x- axis, but
> this doesn't happen.  So,  these and also all the other electrodes
> have small deviations like for example electrode 36 are not align
> whit the electrode 50 in y axis, etc. In this way I can't have a
> symmetrical plot of the electrodes.
> Does anybody have used this layout and have the same problem?
>
> Thanks in advance!
>
> regards,
> Ana Carolina
> ----------------------------------
>
> The aim of this list is to facilitate the discussion between users
> of the FieldTrip toolbox, to share experiences and to discuss new
> ideas for MEG and EEG analysis.
>
> http://listserv.surfnet.nl/archives/fieldtrip.html
>
> http://www.ru.nl/fcdonders/fieldtrip/
>


----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.


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