[Mne_analysis] Negative Weighted Phase Lag Index Values

[Stout, Jeffrey]

We are running analyses on resting state MEG data and we are finding negative values in the weighted phase lag index (wpli) measure.  We have also run this data using the phase lag index (PLI) measure and do not see any values below zero.  I thought that both the PLI and WPLI should be defined from 0 to 1.  Although the negative values tend to be small, we are seeing this across many subjects.

wpli=np.load('connmat_wpli2_debiased13_30hz_run1.npy')

np.min(wpli), np.max(wpli)
Out[22]: (-0.0048496421426467845, 0.14954351856205442)     <<<<<<<<< WPLI minimum value below Zero

pli=np.load('connmat_pli13_30hz_run1.npy')

np.min(pli), np.max(pli)
Out[24]: (0.0, 0.21375066880684856) <<<<<<<<< PLI minimum value equals zero


Is this a correct finding?  Any insight would be helpful.


Thank you,
Jeff Stout
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