How to shift a signal on the $y$-axis to match another signal in MATLAB I have two signals recorded in the time-domain then converted to the frequency domain. These signals are $z$-axis accelerometer measurements recorded from an Arduino 101.

Now visually they are fairly similar (with the peaks and falls sort of lining up), however the difference is in their amplitude, e.g.:



I will be comparing the power of the two signals, so I need them to be in-line with each other, ie. shift either one of the signals to fall around the same area.

I'm not too sure what the terminology for this is, but any help would seriously be appreciated.
Matlab's polyfit function can be used to do linear regression. This can be used to find a linear relationship (offset and gain) that maps one dataset to the other.