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Re: [ferret_users] picking a signal



Hi,
The FFT functions compute their results for each spatial location, that is if the input data is defined in x, y, and t then the result of FFTA(var) will be the FFT frequency spectrum computed at each x,y location. In the language of Ferret functions, the result "inherits" the grid of the input in X, Y, and Z and has a new time axis, the frequency axis created by the funtcion. For the FFT amplitude function:

yes? show function/details ffta
FFTA(A)
   Computes fft amplitude spectra, normalized by 1/N
       Axes of result:
         X: inherited from argument(s)
         Y: inherited from argument(s)
         Z: inherited from argument(s)
         T: created by this function
A: Variable with regular time axis. Specify time explicitly e.g. ffta(var[l=1,120])
       Influence on output axes:
         X: passed to result grid
         Y: passed to result grid
         Z: passed to result grid
         T: no influence (indicate argument limits with "[]")


golla nageswararao wrote:
Hi,
  I mean that I want to pick biweekly signal of FFT
over Indian ocean for quickscat winds. I know only how
to do FFT at a single point. How can I pick up a FFT
signal over entire domain. Please help in this
context.



From,
    G.Nageswara Rao,
  Research Scholar,
  INCOIS,
  Jeeidmetla,
  Hyderabad.


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