covariance in timelockanalysis

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Tue Apr 10 13:09:27 CEST 2007

Hi Sameer,

>               cov: [308x308 double]

> however, cov_avg.cov is essentially all zeros. Is there something I
> am missing here?
> the scaling in the covariance matrix depends on the scaling of your
> signals - if you have the data in units of Tesla (as opposed to
> femto) then of course the covariances are going to be very small.
> This can cause some covariance based analysis methods to "think"
> that your data is rank deficient, etc ...

Since you have 308 channels instead of 306, the units of the channels
will be different since not all of your channels are apparently MEG
channels. The covariance between two channels is in the units of the
two channels, i.e. the EEG-MEG covariance is in units of V*T (Volts
timese Tesla) or uV*fT or something similar.


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