[Eeglablist] Problem running ICA: rank of data lower than the number of input data channels

[Caro Gattei]

Dear all,

I am currently running an experiment with a 32 channel equipment (30+ ext)
and when I try to run ICA in specific subjects I get a message saying that
"EEGLAB has detected that the rank of your data matrix is lower the number
of input data channels. This might be because you are including a reference
channel or because you are running a second ICA decomposition. The proposed
dimension for ICA is 28 (out of 30 channels) rana computation may be
innacurate so you may edit this number below. If you do not understand,
simply press OK"

I found an explanation for the error message on the eegab list that said
that the ranking could be reduced de to low-pass filtering (being that I do
not have a reference  channel and hand't run ICA previously:
 http://sccn.ucsd.edu/pipermail/eeglablist/2012/005110.html

However, I get the same message when I try to run ICA with raw data.

I should mention that we had to reconstruct two channels before the
analysis due to equipment problems. Could that account for part of the
problem?

I must also insist on the fact that even when chennels were reconstructed
for other subjects, I son-t always get the message.

A second question I have is, should I edit the rank to 30 or should I just
run it with 28 components? how would that affect my data?

Best regards,

Caro
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sccn.ucsd.edu/pipermail/eeglablist/attachments/20130911/e69d981e/attachment.html>