[Mne_analysis] Negative Weighted Phase Lag Index Values

Eric Larson larson.eric.d at gmail.com
Wed Jun 14 16:48:20 EDT 2017
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>
> 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.

Eric
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