plotting whitened raw data

✉️ Mailing List Archive (read-only)
1

Hi,

is there an equivalent of evoked.plot_white() for raw data? I would like to compare different covariance methods for whitening empty room data.

Thanks,

Olaf

Olaf Hauk, PhD
MRC Cognition and Brain Sciences Unit
Phone: +44(0)1223 273702
Fax: +44(0)1223 359062
Web: http://www.mrc-cbu.cam.ac.uk/people/olaf.hauk/

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2

hi Olaf,

no there is no such function but it could be added.

Alex

3

Would be interesting to think for a second what would be the normative
prediction in that case (what should be in which value range after proper
whitening) since what is a signal and what is noise is less obvious then,
also potential implications for the power spectrum (could that possibly be
used to summarize the data for visualization?).

Denis

4

If you instead of the usual MNE whitening

y? = lambda^(-1)U^t y

do

y?? = U lambda^(-1)U^t y

the y?? data have their original spatial meaning and the values are SNRs or ?z scores?. Since the whitened data are sphered, they can be rotated in any way. Maybe there is even another more interesting rotation than U.

- Matti

5

If the whitening is applied to the data from which the covariance was computed (e.g. baseline periods in evoked data, the whole data set for continuous data), then I think the prediction should be the same. I would like to compare different covariance methods for empty room data, and such a plot method would be very useful.

Olaf

6

Olaf,

please open an issue if you want this to happen.

Alex