Problem with BESA coordinate system

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Wed Mar 14 10:43:54 CET 2007

Dear Chen,

I have just made some changes to the layout parts of the code. If you
download the latest FT zip file from our FTP server you can see the

I replaced the private/createlayout function by a new main function
PREPARE_LAYOUT. I also updated the LAYOUTPLOT function (actually I
forgot in my previous mail to mention the existence of that
function). The specification of the 2D positions for topo and
multiplotting can now be done more explicitely, and is documented in
prepare_layout. Also the conversion from 3D to 2D locations is also
more easily to recognize. The layoutplot function is there to help in
the debugging.

What now happens is that in the case of specifying cfg.gradfile or
cfg.grad, it will rotate by default with 90 deg. When specifying
cfg.elecfile or cfg.elec, it will NOT rotate. When specifying
cfg.layout, it will just read the *.lay file, or it will read it as
matlab *.mat file without further manipulation, or it will read it as
electrode file and in that case not rotate it. It now would be easy
to explicitely add an cfg.rotate option to the prepare_layout
implementation, but I think that the current version should already
solve your problem.

best regards,

On 13 Mar 2007, at 20:49, Y Chen wrote:

> Hi Robert,
> Thanks for your kind reply. However when I check the createlayout.m
> function, it turns out that in line 229, the coordinate has been
> rotated
> 90 degree (multiply [0 1; -1 0]). For my electrode file, when I remove
> this coordinate transformation, I get the right layout.
> Chen

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