Hilbert envelope correlation about assuming measures positive in bst_henv.m

Hello, Dear brainstorm users and developers! In bst_henv.m script, I really wonder it assumes all measures are non-negative when compute envelope correlation, What about negative correlation?

I apologize for the response delay.
I transferred the question to the authors of the method, but didn't get a reply yet. I will ask again.

@Sylvain @hossein27en @Raymundo.Cassani