Re: Re: Re: change T-axis

["Rongzhen Gao" <gaorz@xxxxxxxxxxx>]

Hi, Jaison, both the example script and mine work.  Now for the reference of other users I made a summary shown as below.

 

There are two variables with different length, and what i want to do is to make them in equal length. Now there are two kind of method to get it.

 

! vars : variable1, N=191 seasons 16-apr-1945:16-oct-1992
!          variable2, N=179 seasons 16-apr-1948:16-oct-1992
!
----------------------------------Method 1:----------------------------------

    define axis/t=16-apr-1948:16-oct-1992/npoints=179 t48to92             
    define grid/t=t48to92 gfile                                           

 

    file/skip=12/grid=gfile/var=variable1 d:\*.asc    !   data for 1945-1947 is skipped from variable1 
    file/var=variable2/grid=gfile  d:\*.asc

----------------------------------Method 2::----------------------------------

     set data monthly_navy_winds  ! dataset available with Ferret

     let l_lo =  13     ! low  value for L  
     let l_hi = 120     ! high value for L

     let u = uwnd[d=1,l=`l_lo`:`l_hi`]  ! extract the subset data
! now extract the time values corresponding to the subset; needed
! only if the original variable is on a calendar time axis

     let t_data = T[gt=uwnd,l=`l_lo`:`l_hi`]

! get other details about the original time axis
     define symbol t_units = `u,r=TUNIT`    ! time units (days/hours...)
     define symbol t_zero  = `u,r=T0`       ! Ref. time
     define symbol t_cal = GREGORIAN  ! JULIAN is also fine          !Ferret 5.5
!    define symbol t_cal   = `u,r=CALENDAR`  ! calendar type           ! higher version
 
! define a destination time axis with these details
 
  define axis/t/T0="($t_zero)"/units=($t_units)/CALENDAR=($t_cal)/from_data tsub=t_data
 
! suppose your original variable is not on a "CALENDAR" time
! axis, then just after extracting the subset, define an abstract "T"
! axis like
! define axis/t=1:`l_hi-l_lo+1`:1 tsub
! and use this in the following sequence of commands
  
! create a new variable "t_stamp"  on the destination grid with XYT grid
!                           put + Z[gz=u]*0 if needed
    let t_stamp = X[gx=u]*0 + Y[gy=u]*0 + T[gt=tsub]  ! destination grid

    let u_t = RESHAPE(u,t_stamp)   ! put variable on the destination grid

! comparison

    list/x=60/y=10/l=1:15 u
    list/x=60/y=10/l=1:3 u_t

    plot/x=60/y=10 u_t, u

 

! now you can use u_t ; for u_t "/L=1" ==> first point on time axis

 

!---------end of example.jnl  written by Jaison----------------------------

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Hi Gao Rongzhen,

 

1. Regarding example

----------------------

 

   Which version of Ferret are you using ?

  `u,r=CALENDAR` will work only with the recent versions (5.6/5.7)

of Ferret. Otherwise use ncdump to see the calendar type; look for

the attribute "calendar=.....", if there is no attribute like that

then it is GREGORIAN, so in Ferret do like this

 

       define symbol t_cal = GREGORIAN  ! JULIAN is also fine

 

2. Regarding your script

------------------------

 

   Without the datasets it is difficult to check your script. Anyway

what seems to me is that:

 

     - both of the datasets are in ascii form, so it is really easy

       to read only the required points (from the bigger dataset)

       rather than reading whole and sub-sizing it in ferret. use

       "SKIP" to skip the first few seasons from the file 

       "sst4503-9211s.asc". Skip the first 12 values from this file

       and read in both the variables to a common grid ..like

       (hope your data is in a single column)

 

       define axis/t=16-apr-1948:16-oct-1992/npoints=179 t48to92

       define grid/t=t48to92 gfile

 

       file/skip=12/grid=gfile/var=coral d:\p12\seasonal\sst4503-9211s.asc

       file/var=wspd/grid=gfile  d:\p12\seasonal\wspd10004803-9211s.asc

 

  Have a trial with the attached jnl file (coral.jnl modified version 

of the script you had send me).

 

With Regards 

 

Jaison

 

-- 

___________________________________________________

 

    Jaison Kurian                           

    Centre for Atmospheric and Oceanic Sciences

    Indian Institute of Science

    B A N G A L O R E   560 012

    Ph: +91-80-3942505

        +91-80-3600450

    Fax:+91-80-3600865

___________________________________________________

 

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