This is discussed also in these two topics:
-
How is the orthogonalization symmetric in the "bst_henv.m" function? - #6 by Raymundo.Cassani
=> This topic concludes that there be can negative values, while in fact, the output values are positive only. -
Hilbert envelope correlation about assuming measures positive in bst_henv.m
=> This one never received any answer
@hossein27en @Sylvain @leahy @Raymundo.Cassani
Some text to explain the positive-only values should probably be added to the documentation for this method: https://neuroimage.usc.edu/brainstorm/Tutorials/Connectivity#Envelope_correlation