How to move a signal to be on the x-axis

I receive sets of data (x,y); they form signal waves but some of signals are waving away from the x-axis. So Im wondering what is the way to move the signal (whether its above or below the x-axis) to be centered on the x-axis? note. the signal waves are in a horizontal trend

Answer 1

[Chunru]

try "detrend".