Y-axis unit of FFT

Newbie
1

Consider the following code:
TVirtualFFT::SetTransform(0);
TH1F *hm = h->FFT(hm, “MAG”);
where h is the original signal with Y-axis unit XXX.

Does the Y-axis unit of hm remain the same as h (i.e., XXX as well)? or is there a scaling factor being applied?

2

Hi,

No the Y axis of the returned histogram is the Magnitude = sqrt(real^2 + im^2) of the FFT output of the transformation. You can also have the real or the imaginary part as output. See the TH1::FFT documentation

Lorenzo

3

I see. Thanks for replying, Lorenzo!
To make sure, this means the unit of the magnitude of the transform is identical to the unit of the original signal?