[FieldTrip] Why does ft_selectdata remove "pow" from sourcedata during statistics?

Schoffelen, J.M. (Jan Mathijs) jan.schoffelen at donders.ru.nl
Sun May 1 18:52:19 CEST 2016

Dear Andreas,

Have you tried it with a more recent version? Also, I would recommend not to use ft_sourcegrandaverage, but to use the syntax ft_sourcestatistics(cfg, source1{:}, source2{:}), assuming you have the single subject data represented in a cell-array of structures, with source1 for condition 1 and source2 for condition 2.


On 24 Apr 2016, at 18:36, Andreas Sauer <sauer.mpih at googlemail.com<mailto:sauer.mpih at googlemail.com>> wrote:

Dear all,

unfortunately, I am having problems to run source statistics on ERF mismatch negativity data (recorded with a 4D system).

With the following data structure as input (output from ft_sourcegrandaverage), fieldtrip gives a warning that it „could not determine dimord of „pow“ in the following data“

pow: [16x37696 double]
dim: [31 38 32]
inside: [37696x1 logical]
pos: [37696x3 double]
time: [1x900 double]
cfg: [1x1 struct]

and later throws an error that „field „pow“ (is) not present in data“. I checked the ft_sourcestatistic script step by step and found out that ft_selectdata removes it after being called by ft_sourcestatistics.

I am using the fieldtrip version from 15/05/2015. I also tried with older versions, one from late 2014 and late 2013, but nothing worked.

Unfortunately, since ft_selectdata removes the field "pow" from the data during the call to ft_sourcestatistic, I can’t put it back in to the structure.

Any help with this (esp. why „pow“ is being removed) is highly appreciated!

Thanks and best wishes,


Dipl.-Psych. Andreas Sauer
Max Planck Institute for Brain Research
Deutschordenstraße 46
60528 Frankfurt am Main

T: +49 69 96769 278
F: +49 69 96769 327
Email: sauer.mpih at gmail.com<mailto:sauer.mpih at gmail.com>
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