[gradsusr] xdef and ydef problem

[Jackie Yip]

Thank you, Arlindo. The problem is solved... there was a mistake in the
argument of re(). But if I was to use the lats4d option you suggested, why
is the input file a ctl instead of the netcdf file of my data? Or is that
input.ctl the same ctl as I'd use to open that netcdf file inside grads
using xdfopen?

Jackie

On 25 April 2011 21:04, Arlindo da Silva <dasilva at alum.mit.edu> wrote:

> On Fri, Apr 22, 2011 at 2:36 PM, Jackie Yip <zheng.yip at mcgill.ca> wrote:
>
>> Hi everyone,
>>
>> I'm using the re() function of GrADs 2.0.a9.oga.1 to regrid my data. As my
>> data is in netcdf format and it has 365 day calendar. I created a descriptor
>> file (.ctl) to xdfopen it. The regridding seem to work fine and I fwrited it
>> out as a grads binary (.dat) file. To view this regridded data, I created
>> another descriptor file. When I tried to view this regridded data on grads,
>> it has a diagonal strip of missing data. This problem disappeared once I
>> have increased my xdef value by 1. Although now the regridded data looks
>> right, I've found that the data shifts down off the map grid with time (e.g.
>> at timestep 2, the data is about 2 gridcells unaligned to the map grid.).
>>
>> Is this a problem related to the ydef in the descriptor file?
>>
>>
> A couple of things to watch for.
>
> 1) make sure grads is not doing any longitudinal wrapping; to be sure do a
> "q file" and "set x 1 $xsize" and $xsize is the size of the x-dimension.
>
> 2) if you fwrite your data (as a plain binary stream) make sure your ctl
> does not specify the file as "sequential" (or vice versa)
>
> Another possibility is to use lats4d.sh to regrid your file. Let
> "newgrid.ctl" be a ctl for a file on the new grid resolution (use "options
> template" so the data file does not have to exist). Then from the shell
> command line issue something like this:
>
> % lats4d.sh -i input.ctl -o output -de newgrid.ctl -func 're(@,1)' -v
>
> By default this will create a netcdf file (output.nc) on the new grid, use
> -format for specifying a different format; "lats4d.sh -h" gives a man page.
>
>   Good Luck,
>
>     Arlindo
>
>
>
>
>
>     Arlindo
>
>
>
>
>
>
>
>
>
>> Jackie
>>
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>>
>>
>
>
> --
> Arlindo da Silva
> dasilva at alum.mit.edu
>
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>
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