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<div dir="ltr"><font color="#000000" size="2" face="Tahoma">Dear EEGLAB users,</font></div>
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<div dir="ltr"><font size="2" face="tahoma">I am using EEGLAB to run an ICA on my EEG data that I acquire in an EEG-fMRI environment to ultimately get rid of the cardioballistogram artifact that is typical for recording EEG inside the strong magnet of an MRI
machine.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">Recently I get a message that reads as follows:</font></div>
<div dir="ltr"><font size="2" face="tahoma">"EEGLAB has detected that the rank of your data matrix is lower [than] 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 57 (out of 62 channels). Rank computation may be inaccurate so you may edit this number below. If you do not understand, simply press OK below."</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">Besides being very thankful for the last sentence, I really do not understand the problem. Actually the number of channels that EEGLAB proposes varies between 57 and 60 (out of the actual 62 channels) for the 6 files
I want to run the ICA on. These files differ only in the stimulus condition, the EEG properties are not changed at all, they are recorded on the same EEG machine (Neuroscan Maglink), with the exact same setup for approximately the same time (about 9:45 minutes
each). So while I of course do expect the EEG to differ in some properties of the EEG signal, i.e. changes in gamma band etc., the recording setup conditions are the same. So I do not see where there would be a systematic mistake in the recording, especially
since I have had the same failure notice on a data set, where I had used the ICA before without any problem and then 2 weeks later, when I wanted to redo the ICA on the same EEG data, where I had only applied a different filter in the Neuroscan software before
running the ICA analysis (a different low frequency filter), I get the same failure notice.</font></div>
<div dir="ltr"><font size="2" face="tahoma">More over, the channels that are not displayed in the channel selection dialog before running the ICA is not systematic, once it was for example the EEG channel F5, once the EEG channel P7.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">The ICA itself gets me great decomposition, I can get rid of the artifact very nicely, I am happy with the resulting data, but I don't like the idea, that I am possibly systematically missing data. I do read the EEG
in a clinical way, I am a medical researcher.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">Any ideas where my mistake could be?</font></div>
<div dir="ltr"><font size="2" face="tahoma">A similar question had been asked in 2011 and 2009, mainly pertaining to a problem of displaying all channels in a 32 bit dataset.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">In case you need screenshots of my problem I will be happy to answer emails to my email-adress directly.</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">Thank you all, I enjoy EEGLAB and its community a lot,</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma">Jan Rémi</font></div>
<div dir="ltr"><font size="2" face="tahoma">Epilepsy and Sleep Center, Department of Neurology,
</font><font size="2" face="tahoma">University of Munich</font></div>
<div dir="ltr"><font size="2" face="tahoma">currently: Department of Neurology, University of Coimbra, Portugal</font></div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
<div dir="ltr"><font size="2" face="tahoma"></font> </div>
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