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Re: [ferret_users] Error to save spectrum and phase of FFT in period unit

Hi -
My apologies. I made an editing error like I think you had done, originally! 

You have commands which define the FFT variables, but the script you had is making a plot so it lists pairs of variables to plot.  It has defined variables including "per", "fft_uwnd", and "FFT_uwndfftp"

So all you need is
!Save fft period unit
save/file=fft_period.nc per[l=1:`FFT_nf`], fft_uwnd

!Save phase in period unit
save/file=phase_period.nc per[l=1:`FFT_nf`], FFT_uwndfftp
Or if you want to rename variables you could do this, but watch out about variable names, there is already a variable called A in the script, so if you do a "LET A = " definition, you'd redefine that existing variable and ruin the calculation.
!Save fft period unit
let AOUT = fft_uwnd
save/file=fft_period.nc per[l=1:`FFT_nf`], AOUT

!Save phase in period unit
let BOUT = FFT_uwndfftp
save/file=phase_period.nc per[l=1:`FFT_nf`], BOUT

On 8/2/2012 3:16 PM, antonio avio wrote:

Thanks Ansley for the reply,
The main goal is to save the fft and phase from spectral analysis which have period unit in x axis.

Yes, I also did the same thing, but i still got the error message,
After compiling i got this error:

**ERROR: command syntax: per[l=1:378], fft_uwnd
          Definition contains multiple expressions
DEFINE VARIABLE A = per[l=1:378], fft_uwnd
Command file, command group, or REPEAT execution aborted

Thanks for the helps,

On Thu, Aug 2, 2012 at 9:36 PM, Ansley Manke <ansley.b.manke@xxxxxxxx> wrote:
You are using "SET_UP per" as if it's a variable name.  The error message is telling you that variable names in Ferret cannot have a space in them.

Do you mean to say this?

!Save fft in period unit
let A = per[l=1:`FFT_nf`], fft_uwnd

On 8/2/2012 10:58 AM, antonio avio wrote:
I wonder why I got this error when i wanted to save the results of FFT analysis (period unit not frequency) in different nc files:

!Save fft in period unit
let A = SET_UP per[l=1:`FFT_nf`], fft_uwnd
 !-> DEFINE VARIABLE A = SET_UP per[l=1:378], fft_uwnd
 **ERROR: command syntax: SET_UP per[l=1:378], fft_uwnd
          SET_UP before per[l=1:378] is illegal
DEFINE VARIABLE A = SET_UP per[l=1:378], fft_uwnd
Command file, command group, or REPEAT execution aborted

Here is my command:

!converting to Period
! Get the frequency increment used in the FFT.
      LET FFT_nf = `fft_uwnd,return=lend`
      LET FFT_nyquist = 0.5
      LET FFT_freq1 = FFT_nyquist/ FFT_nf

! Define a frequency axis.
      DEFINE AXIS/T=`FFT_freq1`:`FFT_nyquist`:`FFT_freq1` FAXIS
      DEFINE GRID/T=FAXIS gfftfreq
      LET a = T[g=gfftfreq]

! Define the period from the frequency axis.
      LET per = 1./a

! Plot period vs FFT Amplitudes showing the first 24 months where most of the energy is.
! The PPL commands clean up the appearance of the plot.

      PLOT/VS/LINE/HLIMITS=0:32:2/TITLE="Amplitude Spectrum"/SET_UP per[l=1:`FFT_nf`], fft_uwnd
      PPL XFOR (I2)
      PPL XLAB Period, months/cycle
      PPL YLAB 
      PPL PLOT
! Compute and plot the phase using fftp.

      LET FFT_uwndfftp = fftp(fft_u[l=1:757])
      SET VARIABLE/TITLE="FFT Phase"/UNITS="deg" FFT_uwndfftp

      SET VIEW ll
      PLOT FFT_uwndfftp

      SET VIEW lr
      PLOT/VS/LINE/HLIMITS=0:32:2/TITLE="FFT Phase"/SET_UP per[l=1:`FFT_nf`],FFT_uwndfftp
      PPL XFOR (I2)
      PPL XLAB Period, months/cycle
      PPL YLAB Deg
      PPL PLOT

!Save fft period unit
let A = SET_UP per[l=1:`FFT_nf`], fft_uwnd
save/file=fft_period.nc A

!Save phase in period unit
let B = SET_UP per[l=1:`FFT_nf`], FFT_uwndfftp

Thanks for your help.


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