[FieldTrip] ft_selectdata - automatic channels sorting

[Martina Postorino]

Dear Jan-Mathijs,

thanks for your quick reply.
I did not apply the ft_selectdata to the 'stat' output (there the channels
were selected in the cfg.channel field of the ft_timelockstatistics
function). I only apply that function to my ERP dataset to select a subset
of channel on which I wanted the information stored in stat.mask to be
plotted, this is why the order of channels was inconsistent (I am sorry, I
know it is a bit hard to explain).

By the way, I am following this issue on the Bugzilla website.

Thanks again,
best regards.

*__________________*

Martina Postorino, M.Sc
Phd program in Medical Life Science and Technology

Neuroimaging Center (TUM-NIC)
Technische Universität München, Klinikum Rechts der Isar



2014-06-25 8:55 GMT+02:00 jan-mathijs schoffelen <
jan.schoffelen at donders.ru.nl>:

> Hi Martina,
>
> I agree that the sorting of the channels is somewhat annoying, and an
> unexpected feature in the coding. Presently we are looking into how to
> address this.
>
> Yet, the sorting that is applied to the list of channels is consistently
> applied to all fields that contain numeric data. In your case I don’t
> understand your statement that the mask stays unsorted. Is there any way
> you are able to verify that? If I run the following simple simulation
> everything is reordered, also the ‘mask’-field.
>
> stat.label={‘B’;’A’;’C’};
> stat.stat=repmat([1:3]’,[1 2]);
> stat.mask=stat.stat;
> stat.prob=stat.stat;
> stat.time=[1 2];
> stat.dimord=‘chan_time’;
>
> stat2=ft_selectdata([],stat);
>
> If I now do:
>
> stat2.label
>
> I get
>
> ans =
>
>   ‘A’
>   ‘B’
>   ‘C’
>
> and when I do:
>
> stat2.stat
>
> I get
>
> ans =
>
>   2 2
>   1 1
>   3 3
>
> and when I do:
>
> stat2.mask
>
> I get
>
> ans =
>
>   2 2
>   1 1
>   3 3
>
> Conslusion: the mask is also re-ordered. In other words, the rows in the
> numeric data fields are still consistent with respect to one another.
>
> If you want to stay informed about this issue, I suggest you to create an
> account on bugzilla.fcdonders.nl, and add yourself to the cc-list of bug
> #2597.
>
>
> Best wishes,
> Jan-Mathijs
>
>
> On Jun 23, 2014, at 4:14 PM, Martina Postorino <
> martina.postorino at gmail.com> wrote:
>
> Dear all,
>
> I recently encountered a problem using the function ft_selectdata to
> select a subset of channels from my EEG dataset.
>
> I found out that in the output of the function ft_selectdata, channels are
> sorted alphabetically. For me, that represents a problem since I would like
> to plot the results from a cluster based permutation test using the
> information stored in stat.mask (in which the order of channels is in line
> with the original order of channels, i.e. not alphabetically) on the ERP
> grandaverage of specific electrodes selected with ft_selectdata, to see
> which time points are significantly different between my experimental
> conditions. Due to the different orders of the channels, the mask is
> plotted over the wrong channels.
>
> Is there a way to avoid that the function automatically sorts the labels
> of the channels alphabetically?
>
> I have already tried the different versions of ft_selectdata
> (ft_selectdata, ft_selectdata_old, ft_selectdata_new) and updated my
> Fieldtrip version to the last one available. Nothing changed.
>
> This is the code I use:
>
> [stat] = ft_timelockstatistics(cfg, ERP_pain_bp_GA, ERP_buttonpress_GA);
>
>  %plotting
>
> cfgp = [];
> cfgp.channel = {'Cz'; 'CPz', 'Pz', 'CP1'. 'CP3', 'CP2', 'CP4'};
> cfgp.avgoverchan = 'no';
> cfgp.latency = [-1 1];
> ERP_pain_bp_GA_red = ft_selectdata_new(cfgp, ERP_pain_bp_GA);
> ERP_buttonpress_GA_red = ft_selectdata_new(cfgp, ERP_buttonpress_GA);
>
> % average data across subjects
>
> cfgp = [];
> cfgp.keepindividual = 'no';
> ERP_pain_bp_GA_avg = ft_timelockanalysis (cfgp, ERP_pain_bp_GA_red);
> ERP_buttonpress_GA_avg = ft_timelockanalysis (cfgp,
> ERP_buttonpress_GA_red);
> % ERP_pain_GA_avg = ft_timelockanalysis (cfg, ERP_pain_GA_red);
>
> ERP_pain_bp_GA_avg.mask = stat.mask;
> ERP_buttonpress_GA_avg.mask = stat.mask;
> % ERP_pain_GA_avg.mask = stat.mask;
>
> % do the plotting
>
> cfgp = [];
> cfgp.maskparameter = 'mask';
> cfgp.maskstyle = 'box';
> cfgp.layout = layout_easycap_painlabmunich;
>
> ft_multiplotER(cfgp,ERP_pain_bp_GA_avg, ERP_buttonpress_GA_avg);
>
> Thanks in advance!
>
> ___________________________________________
>
> Martina Postorino, M.Sc
> Phd program in Medical Life Science and Technology
>
> Neuroimaging Center (TUM-NIC)
> Technische Universität München, Klinikum Rechts der Isar
>
>  _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
>     Jan-Mathijs Schoffelen, MD PhD
>
> Donders Institute for Brain, Cognition and Behaviour,
> Centre for Cognitive Neuroimaging,
> Radboud University Nijmegen, The Netherlands
>
> Max Planck Institute for Psycholinguistics,
> Nijmegen, The Netherlands
>
> J.Schoffelen at donders.ru.nl
> Telephone: +31-24-3614793
>
> http://www.hettaligebrein.nl
>
>
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> fieldtrip at donders.ru.nl
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>
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