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<br>Dear all,<br><br>I have a question related to the rank of the covariance matrix<br>used for the beamformer.<br><br>I preprocessed my data using ICA to reject EOG and ECG component (typically<br>between 2-4 components). This however, leads to a reduction in the rank<br>of the covariance matrix and I get a warning using ft_sourceanalysis<br>saying that my covariance matrix is rank deficient because rank(COV) < Nchannels.<br><br>I would like to know, how much of a problem and how serious this can be.<br><br>The way I understand things, this should only cause trouble if the number<br>of active sources exceeds the number of linearly independent rows of the covariance matrix?<br>Is this assumption correct? <br><br>Is there some step in the ft_sourceanalyis pipeline that assumes that the number of<br>sources is equal to the number of channels, and that could bias the computation<br>of the beamformer? I mean in that case I would have more sources than channels<br>and thus the beamformer would fail.<br><br>Would be great if someone could help me to figure this out.<br><br>Cheers,<br>Fred<br><br><br><br><br>-- <br>Frédéric Roux, PhD student<br>Department of Neurophysiology<br>Max Planck Institute for Brain Research<br>D-60529 Frankfurt am Main<br>Frederic.Roux@brain.mpg.de<br>+49(0)69630183225<br><br><br> </div></body>
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