Hi Rick,
Thank you so much for your reply. I had been talking with Bob about this topic, and the problem was more specific than I thought. Even though the problem is solved, I would like to post what happened because this could be useful for other users.
Basically, I was trying to use "sub bands" which are bands with very short frequency ranges. The cause of the error in the program was because I tried to band pass at these very low frequency (0.002 - 0.01 Hz). Unfortunately, that removed all the independent components in the signal, leaving nothing behind. At that point it is not possible to get any valid statistics. So, the given error is convenient in the way to warn the users that their results are not robust at that point, which is something great.
Kind regards,
Karel
