[Mne_analysis] Negative Weighted Phase Lag Index Values
andrea.brovelli at univ-amu.fr
Thu Jun 15 02:49:26 EDT 2017
Suggestion: in Fieldtrip, the WPLI is implemented in its signed version,
it is not the eq.8 of Vinck' paper, which is bounded [0, 1].
The estimator is (line 73 in ft_connectivity_wpli.m
Maybe the MNE code got inspiration from it.
Le 14-Jun-17 à 10:48 PM, Eric Larson a écrit :
> this also occurs when computing the debiased squared wpli, where
> there should undoubtedly be no negative values (unless the
> debiasing does something strange that I'm not aware of), just FYI.
> From what I recall the debiasing can indeed produce (generally small)
> negative values, so that at least I would expect. From Vinck et al., 2011:
> If the WPLI exceeds the PLI, then the debiased WPLI-square
> estimator will be negatively biased for small sample sizes.
> The WPLI, however, doesn't have this characteristic, and from what
> I've seen in a brief look at the MNE code, I'm not sure where it could
> come from (based on where we use abs()). So a minimal example would
> help us track it down.
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