Re: [idvusers] IDV formula for gradient of scalar field

  • To: Valentijn Venus <venus@xxxxxx>
  • Subject: Re: [idvusers] IDV formula for gradient of scalar field
  • From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
  • Date: Thu, 14 May 2009 06:14:35 -0600
Hi Tyn-


Valentijn Venus wrote:
Can the same be used on for gradient in 3 dimensions ?

No, it's just the horizontal gradient:

   GRAD ( S ) = [ DDX ( S ), DDY ( S ) ]

Don

-----Original Message-----
From: idvusers-bounces@xxxxxxxxxxxxxxxx
[mailto:idvusers-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Don Murray
Sent: Friday, May 01, 2009 9:06 PM
To: Stuart Wier
Cc: IDV Users
Subject: Re: [idvusers] IDV formula for gradient of scalar field

Hi Stu-

Stuart Wier wrote:
I need to make an IDV formula to make the gradient of a 2d scalar field (a new 2d vector field), and also the magnitude of the gradient as a new scalar field. Anyone know how to do that offhand?

You can use the grad(S) python procedure in the griddiag.py module to
compute the gradient.  Use the mag(V) procedure to compute the magnitude
of the resulting vector:

mag(grad(S))

You can use the Grid->Define a grid diagnostic Formula to try this on
the fly, or create a formula.

All the jython procedures are documented at:

http://www.unidata.ucar.edu/software/idv/docs/userguide/tools/JythonLib.
html

(I just noticed that the mag function on that page is not formatted
correctly.  I'll fix that for a future release).

Don
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************

_______________________________________________
idvusers mailing list
idvusers@xxxxxxxxxxxxxxxx
For list information, to unsubscribe, visit:
http://www.unidata.ucar.edu/mailing_lists/
Internal Virus Database is out of date.
Checked by AVG - http://www.avg.com
Version: 8.0.176 / Virus Database: 270.9.17/1845 - Release Date:
12/12/2008 9:02 AM
International Institute for Geo-Information Science and Earth Observation (ITC)
Chamber of Commerce: 410 27 560

E-mail disclaimer
The information in this e-mail, including any attachments, is intended for the 
addressee only. If you are not the intended recipient, you are hereby notified 
that any disclosure, copying, distribution or action in relation to the content 
of this information is strictly prohibited. If you have received this e-mail by 
mistake, please delete the message and any attachment and inform the sender by 
return e-mail. ITC accepts no liability for any error or omission in the 
message content or for damage of any kind that may arise as a result of e-mail 
transmission.

--
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************