Re: virtual variable in LAS

[Zhangfan Xing <xing@xxxxxxxxxxxxxxxxxxxx>]

Hi, Jon,

Thanks a lot. This time it works.

However I need to confirm:

> level and none is defined for the 'u_v' variable.  The simple fix is to
> define your variable like this:
> 
>         <u_v units="M/S" name="u v diff"
> url="file:/mnt/sde1/datasets/adjoint/
> Vave.des>

The url value here is faked in order to fool las parser?
I reasoned that the *.jnl script would preempt *.xml with regard
to which real varaibles are to be used.

> ! We must define var$2_grid for use in differencing.
> ! This grid must reference a file variable: one that actually
> ! exists in dataset 'dset' as opposed to a virtual variable
> ! created with an expression involving other variables.
> define grid/like=Uave[d=1] var1_grid_

Does var1_grid_ defines a default grid for
whatever variables to be manipulated below?
  
> 
> ! Any extra work: defining virtual variables, regridding, etc
> ! should be done at this time.
> 
> let/title="u and v Difference"/units="M/S" u_v = Uave[d=1] - Vave[d=2]

What does "d=1" and "d=2" mean?

I should have read ferret manual in depth ;-<

Zhangfan