Fwd: [ferret_users] time axis

I have a ascii file with columanr data as defined in file velplot.dat(below in the code)
I am plotting the field value @ a given time t.

1. I am advised to define im,jn,tm values which are no of corresponding axis data points on a curvilinear grid.
I am not using them anywhere in the code. do I have to??... as i define them again in "define axis" line making
"let im=" lines becoming redundant!

2.can I plot with the definition of grid etc, the field value @ a given longitude by
    giving the command as

     fill/y=200 tauy,lat,T
     go land

3. which one is better shade or fill command for this type of problems

with regards

I wanted to plot the data for the month of june(ie t=6), it gives the error in time axis
my jnl file is as below
-----------------------------------------------------------------
let im=600 ! no of longitudes points (not longitude values)
let jm=375 ! no. of lalitude points (not latitude vales)
let tm=12   ! no. of month points

define axis/x=1:600:1 xindex
define axis/y=1:375:1 yindex
define axis/T=1:12:1 time
define grid/x=xindex/y=yindex/T=time xyt_grid

file/grid=xyt_grid/var="lon,lat,time,taux,tauy" velplot.dat      ! for 3D

set variable/units=degrees_east lon
set variable/units=degrees_north lat
set variable/units="month" time
set variable/units="m2/s" taux
set variable/units="m2/s" tauy

set viewport ul
fill/time=6 taux,lon,lat
go land

set viewport ur
fill/time=6 tauy,lon,lat
go land

set viewport lr
vec/time=6 taux,tauy
go land

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

with regards
CS