[FieldTrip] Can I use FieldTrip plotting on an existing data?

Eelke Spaak eelke.spaak at donders.ru.nl
Wed Nov 21 08:46:22 CET 2012

Dear Liad,

FieldTrip data structures are just Matlab structures, so with some
custom Matlab code you should be able to convert any arbitrary data
matrix into FT style. The data you have resembles the output of FT's
ft_timelockgrandaverage function, with keepindividual='yes' specified.
It should look something like this to be compatible with FT:

data =

         label: {152x1 cell} % channel labels
           avg: [152x900 double] % grand average, chanXtime
           var: [152x900 double] % variance, chanXtime
          time: [1x900 double] % time axis, in seconds
    individual: [10x152x900 double] % subjXchanXtime, individual averages
        dimord: 'subj_chan_time' % keep as is, dimensionality ordering
for the fields

Alternatively, you could put the difference data in a 'simple'
(single-subject) timelock data structure, which would also allow it to
be plotted. This approach is probably the easiest, if all you want to
use FT for is plotting the topography of difference. Have a look at
for how to create a simple timelock data structure.


On 21 November 2012 07:01, liad glz <liad.glz at gmail.com> wrote:
> I have two matrices that include EEG data for two experimental conditions
> (channelsXtimepointsXsubjects). The data has already been preprocessed. I
> would like to use FieldTrip in order to plot topographic maps for the
> difference between the conditions, and I see that the function requires many
> input variables that were manufactured by the previous functions in
> FieldTrip. Does that mean that I cannot use a function without running all
> the previous ones on the raw data?
> Many thanks
> Liad
> _______________________________________________
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> fieldtrip at donders.ru.nl
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