[FieldTrip] problem with ICA

[Aaron Schurger]

Sounds like you may have done something to your data, like
interpolating channels, before you ran ICA. It is OK to filter your
data before running ICA, and some other operations are OK too, but if
you do anything that mixes activity from different channels in any
way, then you can run into problems with ICA (and results from ICA can
be invalid).
Aaron

On Thu, Jan 16, 2014 at 1:22 PM, Hwee Ling Lee <hweeling.lee at gmail.com> wrote:
> Dear all,
>
> I've collected data using a 128 channel EEG cap, and I tried to perform ICA
> on the data. However, I got an error message with fieldtrip on Matlab.
> Here's the error message:
>
> the input is raw data with 127 channels and 1 trials
> selecting 123 channels
> baseline correcting data
> scaling data with 1 over 148.247820
> concatenating data.
> concatenated data matrix size 123x2789000
> starting decomposition using runica
>
> Input data size [123,2789000] = 123 channels, 2789000 frames/nFinding 123
> ICA components using logistic ICA.
> Decomposing 184 frames per ICA weight ((15129)^2 = 2789000 weights, Initial
> learning rate will be 0.001, block size 75.
> Learning rate will be multiplied by 0.9 whenever angledelta >= 60 deg.
> More than 32 channels: default stopping weight change 1E-7
> Training will end when wchange < 1e-07 or after 512 steps.
> Online bias adjustment will be used.
> Removing mean of each channel ...
> Final training data range: -3.46556 to 6.39436
> Computing the sphering matrix...
> Starting weights are the identity matrix ...
> Sphering the data ...
> Beginning ICA training ...
> Data has rank 119. Cannot compute 123 components.
> the call to "ft_componentanalysis" took 148 seconds
>
> Could someone please let me know what went wrong?
>
> Thanks!
>
> Cheers,
> Hweeling
>
>
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip



-- 
Aaron Schurger, PhD
Senior researcher
Laboratory of Cognitive Neuroscience
Brain-Mind Institute, Department of Life Sciences
École Polytechnique Fédérale de Lausanne
Station 19, AI 2101
1015 Lausanne, Switzerland
+41 21 693 1771
aaron.schurger at epfl.ch
http://lnco.epfl.ch/