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20030807: Questions in creating formula in IDV!!

To: address@hidden
From: =?big5?q?LEONG=20IVAN?= <address@hidden>
Subject: Questions in creating formula in IDV!!
Organization: ?
Keywords: 200308070810.h778AeLd011284 IDV formula


Ivan-


     I get a problem when I try to create a formula in
IDV.  Actually I am going to write a formula to
calculate the layer thickness between 500hpa and
850hpa level. Formula creating is easy but the problem
come out when I gonna to choose the actual
geopotential height data from data source in different
level.  In the select actual data window, what I've
seen just have the geopotential height which include
several level but don't have different level
geopotential height individually. So, how can i do?


In the latest IDV release, a system formula is available to
allow you to do this already.  From the DataSelection window,
load in your DataSource with the geopotential height grid.
Then, select the Formulas datasource and under the System
category, select Layer Difference. Then select the type of
display you want (e.g., Contour Plan View).  A dialog will
pop up that will allow you to input your layer boundaries.
Put in 500 for the top and 850 for the bottom.  Then select
the geopotential height field in the next dialog and press
OK.

Alternatively, you could create a new formula which would
pass in the parameters directly instead of having the
prompting dialog.  The formula would be:

DerivedGridFactory.createLayerDifference(a, 500, 850)

After loading in your dataset with the geopotentia height
(or whatever parameter you want to layer difference), select
the formula and the display type and it will prompt you for
the parameter you want to substitute for variable "a".


     The other question is, can you provide any other
source like books, documentations or homepages which
are introduced IDV more deeper than user's guide of
IDV which can be found from
http://www.unidata.ucar.edu.


At present, the only documenation we have is the User Guide
and tutorial at:

http://my.unidata.ucar.edu/content/software/IDV/docs/UserGuide

Thanks for your interest in the IDV.

Don Murray
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