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Some questions about function FFTA and FFTP



Dear ferret users:
I am using FFTA to do some research. I just want to use different units of T axis.
I have read the user's guide. But I can not understand them well.
In the ferret guides , there is the following description about FFTA

"The units of the returned time axis are "cycles/Dt" where Dt is the time unit of the input axis. The Nyquist frequency is yquist = 1./(2.*boxsize), and the frequency axis runs from freq1 = yquist/ float(nfreq) to freqn = yquist "

question 1.
the returned time axis should be day because the time unit of my input axis is day. However the actual returned time axis is hour.
question 2
what does Nyquist frequence mean? What is the boxsize?

actually I am not very clear to the process of converting the time axis into what I need. For example, from cycle/day to cycle/month
ok ,that is the problme Thanks a lot

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