[Eeglablist] value of PCA pre-processing before running ICA on EEG data?
arno
arno at salk.edu
Thu Aug 3 14:14:21 PDT 2006
> There is no accepted rule. If you 'n' sample points, you should use no
> more than sqrt(n) "channels" (so if you have more than sqrt(n) channel
> in your data, you use PCA to reduce the dimensionality). This is because
> there is number_channel^2 values in the weight matrix so you need at
> least one value in the data (on time frame) per value in the matrix. In
> our experience, it is good to have number_channel^2<sqrt(n/20).
>
Above, the correct statement if "nc" is the number of channels and "ns"
the number of sample point is
nc < sqrt(ns)
and in general it is good to have
ns > 20*nc^2 (or nc < sqrt(ns/20))
Thanks to Jeff Eriksen for pointing that out to me,
Arno
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