[GEMPAK #JUX-591354]: GEMPAK - problem using sub() function with two datasets

Jon,

I've been out of the office on vacation, so pardon the delayed response.

The GDATTIM = last is your problem since it refers to the "last time"
in the first file, and that time soesn't exist in your second file for which 
you are 
asking for HGHT+2.

Instead, you want to use an inline qualifier for the time of the second file.

In GDPLOT2 for example, it can be as simple as:

GDATTIM = f006
GDPFUN   = sub(hght,hght^f006+2)

The difference hyere is that GDATTIM referes to a time that will be expanded 
from the 
times available in the first file, whereas using the "^" and "+2" force the 
function to
use the time matching from the second file.

One other note, I'd be careful about using "last" since it could produce 
unintended
side affects if you were to get some other times in your grid file (even though 
you have
individual forecast files shown below...so you are OK in this case).

Steve Chiswell
Unidata User Support

> Institution: Weathernews
> Package Version: 5.9.3
> Operating System: Red Hat Linux 2.4.9
> Hardware Information: Pent. 4 256MB RAM 40GB HDD
> Inquiry: I'm trying to plot the difference between two parameters such as 
> surface pressure or 500mb heights between two different runs of the GFS.  
> However when I run this through gdcntr, gdplot3, or try to produe ascii 
> output with gdlist I get the same error:  Input grid HGHT ^070727/0000F006 
> @500 %PRES in SUB cannot be found.  I've copied the entire gdcntr setup 
> below, please let me know if I'm missing something:
> 
> Thanks,
> Jon Oxtoby
> 
> GEMPAK-GDCNTR>l
> GDATTIM  = last
> GLEVEL   = 500
> GVCORD   = pres
> GFUNC    = sub(hght,hght+2)
> GDFILE   = 2007072700f006_gfs.gem+2007072706f006_gfs.gem
> CINT     = 0
> LINE     = 5
> MAP      = 3/1/1
> MSCALE   =
> TITLE    = 1
> DEVICE   = xw
> SATFIL   =
> RADFIL   =
> IMCBAR   =
> PROJ     = mer
> GAREA    = hi
> IJSKIP   =
> CLEAR    = y
> PANEL    = 0
> TEXT     = 1
> SCALE    = 999
> LATLON   = 0
> HILO     =
> HLSYM    =
> CLRBAR   =
> CONTUR   = 3/3
> SKIP     = 0
> FINT     =
> FLINE    =
> CTYPE    = c
> LUTFIL   = default
> STNPLT   =
> 
> 
> 
> 


Ticket Details
===================
Ticket ID: JUX-591354
Department: Support GEMPAK
Priority: Emergency
Status: Closed