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

!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

!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