Hi Mubashar
You can change the definition of the time axis with a DEFINE AXIS
command, using the name of the time axis from the file. Then the
data will be used as if it were on the new time axis. What happens
is that the data in the file will be interpreted using the time
information in the new time axis. The old definition is lost to
Ferret during that session, but the input file you are reading is
unchanged. So, let's make an example:
! define a time axis and set up a variable on that
axis
! Write it to an example file
yes? define axis/t=1-jan-1990:31-dec-1999:1/units=days
time
yes? let var = sin(t[gt=time]/100)
yes? plot var
yes? save/clobber/file=timevar.nc var
yes? cancel variable/all
yes? cancel axis time
! Now open the file, as if we are in a new Ferret
session.
yes? use timevar.nc
yes? plot var ! it's on the 1990-1999 time axis
! redefine the time axis. The last bit of syntax gets
the name
! of the time axis for the variable "var".
yes? define axis/t=1-jan-2000:31-dec-2009:1/units=days
`var,return=taxis`
Replacing definition of axis TIME
*** NOTE: grid used by data set timevar
*** NOTE: Redefinition may alter apparent contents of
data set
yes? plot var ! it's on the 2000-2009
time axis
yes?
save/clobber/file=timevar2000.nc/t=1-jan-2008:31-dec-2009
var
Try some more experiments. What if you redefine the axis like this
(an axis with a lot more coordinate points)? The data will be read
onto the first part of the axis
yes? cancel data/all
yes? use timevar.nc
yes? define axis/t=1-jan-2000:31-jan-2001:1/units=minutes
`var,return=taxis`
yes? plot var
How about this one:
yes? cancel data/all
yes? use timevar.nc
yes? define axis/t=1-jan-2000:1-jan-2002:1/units=days
`var,return=taxis`
yes? plot var
On 1/9/2013 2:37 PM, Star Physicist
wrote:
Dear Ferret users,
I am new to FERRET and wanted to modify time axis in my netcdf
file. I have a netcdf file (with many variables) containing
monthly data from jan1990 to dec1999. Can I create a netcdf file
using FERRET (having all variables) after modifying the time
axis to jan2000 till dec2009 instead of jan1990 to dec1999.
Thanks,
Mubashar
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