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Re: Question about @AVE
HI, Ansley
Thank you for your help. I used show grid t2m to check the longitude
axis and it turned out a modulo axis. But I still don't know how to do the
average. Suppose I want to calculate the mean t2m of grids where I=1:5, I
should use the command
yes? let at2m=t2m[I=1:5@AVE]
But if I want to calculate the mean from I=1:5 plut I=60:64, should I use
the command like this
yes? let at2m=t2m[I=60:5@AVE]
Thank you again for your help.
Ming
On Wed, 11 May 2005, Ansley Manke wrote:
> Hi Ming,
> If you make sure that the longitude axes that you are using are defined
> as modulo axes, then Ferret will automatically take care of averaging
> across the branch point where it wraps around the earth. When you open
> your dataset, you can check whether the input data is on a modulo axis
> with SHOW GRID varname
>
> yes? show grid t2m
>
> The first few lines will have something like this
>
> GRID GNAME
> name axis # pts start end
> LONAX LONGITUDE 64mr
>
>
> If the m is not present after the number of points in the x axis, then
> the axis is not a modulo axis, and Ferret will not wrap around when
> making computations. You can change the setting with a SET AXIS
> command. If the axis name is LONAX, the command is
>
> yes? set axis/modulo lonax
>
> Also when you define the longitude axes of your new grids, use the
> /modulo qualifier:
>
> yes? define axis/x=0:360:10/modulo xax10
>
> Ansley
>
> Ming Yang wrote:
>
> >Hi, folks
> > I have a Netcdf dateset like this:
> > name title I J K L
> > T2M Temperature at 2 Meter 1:64 1:32 ... 1:12000
> >
> >
> >The I coordinate represents longtitude. I would like to use @AVE transfromation
> >to compute the average value of the variable T2M over several grids, but
> >the problem is the grids I would like average include the 0
> >longitude, So that in the @AVE transfromation I have to include I=60:64
> >as well as I=1:5. I am wondering what is the easiest way to do this
> >calculation in ferret? Thank you in advance.
> >
> >Best,
> >Ming
> >
> >
> >
> >
> >
>
>
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