[Eeglablist] ICA runs slowly and returns complex numbers

[Ilana Podlipsky]

Dear Arno,

Judging by the ICA output in Matlab the solution converges but very very
slowly.
I use bipolar montage, each electrode is referenced to its neighbor. I use
64 electrodes recorded with one reference electrode and convert  it to 85
differential channels off line. ICA detects rank 57 but I changed it
manually to 64 since this is the original number of channels, is that
correct?
Meanwhile I tried binica on the same computer running Ubuntu, and it runs
much faster (in 20 minutes). I would still like to resolve this issue
because I'd prefer to work on Windows.

Thanks,
Ilana



On Wed, Nov 20, 2013 at 6:59 PM, Arnaud Delorme <arno at ucsd.edu> wrote:

> Dear Ilana,
>
> did your ICA solution converge (meaning that the weight difference
> decrease with time). This might be the issue.
> Also, are you using average reference or linked mastoid. In this case, the
> data matrix rank is the number of channels minus 1. ICA tries to detect
> this automatically but sometimes fails. You then have to manually reduce
> the number of dimension by 1 when running ICA. If you have 64 channels, in
> the edit box for running ICA (where there is already 'extended', 1) you may
> add 'pca', 63.
>
> Best,
>
> Arno
>
> On Nov 12, 2013, at 11:54 PM, Ilana Podlipsky <ilana.mlist at gmail.com>
> wrote:
>
> > Hi All,
> >
> > Since I've recently changed my computer ICA in eeglab runs very very
> slowly and returns complex numbers.
> > On my previous computer, on the same data I ran the same ICA  within an
> hour or two. On the new computer the same ICA takes more than 24 hours,
> After 512 steps it returns this message :
> >
> > Sorting components in descending order of mean projected variance ...
> > Warning: Matrix is close to singular or badly scaled.
> >          Results may be inaccurate. RCOND = 6.956943e-019.
> >
> > When I try to plot the ICA activations I don't see any traces and when I
> look into the EEG.icaact matrix I see only complex numbers. Tried both
> runica and binica.
> > This has never happen to me with the old computer on the same dataset.
> > Both the old and new computer run Win7 64bit, matlab 2008a and eeglab
> 12. The hardware of the computers is different.
> >
> > What could be the reason for this, and what can ?I do to solve this?
> >
> > Thanks for the help,
> > Ilana
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