[Thread Prev][Thread Next][Index]

Re: [ferret_users] Reg: period calculation in FFT



Hello,

Here is the documentation for FFTA,

https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/variables-xpressions/XPRESSIONS#_VPINDEXENTRY_345

It says
...   the units of the returned time axis are "cycles/Dt" where Dt is the time unit of the input axis. 

So you still use 1./a where a is a variable containing the time coordinates of your time axis, and the units will be cycles/hour. 

-Ansley



On 7/18/2018 9:13 PM, milik a wrote:
Dear ferreters,

Please help me and thanks in advance.

I have a query regarding defining period  in FFT. The example below is for monthly navy winds in ferret.
! Define the period from the frequency axis. (From FFT demo)
      LET per = 1./a

Here 1./a for monthly data (If I am correct). If I have hourly data, what should the the value in place of 1.

And also if it is weekly and 15 days data what should be taken. I have both hourly data and 15 days data. I am confused in taking this value. 

Please help.
Thank you.
Milika



[Thread Prev][Thread Next][Index]
Contact Us
Dept of Commerce / NOAA / OAR / PMEL / Ferret

Privacy Policy | Disclaimer | Accessibility Statement