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

liad glz liad.glz at gmail.com
Fri Nov 23 21:58:38 CET 2012

Dear Eelke,

Thank you for your reply. It was indeed the answer I was hoping to get.
I still have some questions about the variables though:
1. When you refer to 'var', do you mean SDs? SEs? some other measure of
variance that I should calculate?
2. In the webpage you referred me to, i saw that I should also define
"dof"; I gather that in the case of average across subjects, this refers to
the number of subjects. Then, it will be a matrix of CHANxTIME, where all
values are identical to the number of subjects. Is this correct?
3. What about the grad & cfg fields? How should I generate these?

Many thanks again for your help

On Tue, Nov 20, 2012 at 11:46 PM, Eelke Spaak <eelke.spaak at donders.ru.nl>wrote:

> 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
> http://fieldtrip.fcdonders.nl/faq/how_are_the_various_data_structures_defined
> for how to create a simple timelock data structure.
> Best,
> Eelke
> 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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