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

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

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:

Hallo,

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,

Antonio

On Thu, Aug 2, 2012 at 9:36 PM, Ansley Manke <ansley.b.manke@xxxxxxxx> wrote:

Hi
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:

Hallo,

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:

[SNIP]

!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.

 SET VIEW ur

      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

save/file=phase_period.nc B 

!**********************************************************************************

Thanks for your help.

Antonio.