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Re: GRIDDATA woes [message #59031 is a reply to message #59026]

Tue, 04 March 2008 11:49

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Kenneth P. Bowman writes:

> This problem looks just like the one David Fanning was working
> on recently, and here is an outline of the solution
>
>> Assuming that your data is 2-D (x = longitude and y = latitude), create
>> the grids that you want to interpolate to
>> nx = 360
>> ny = 181
>> x �= FINDGEN(nx)
>> y �= -90.0 + FINDGEN(ny)
>> Compute the "interpolation coordinates" from the original grid
>> j �= VALUE_LOCATE(y_original, y)
>> yj = j + (y - y_original[j])/(y_original[j+1] - y_original[j])

This works OK, I think, if the values you wish to interpolate
to are completely contained within the bounds of the original
vectors. But, suppose the original array was 180x90 and
I want to interpolate from 360x180. Then, the beginning
and ending values in the vectors I want to interpolate to
are outside the bounds of the original vectors. When
I go to find the "interpolation coordinates", I encounter
divide by zero errors and get infinities in my vectors.

Do you have a way of handling this situation? I mention
this because in the perverse CCCMA climate model I am
using, the longitude vector is evenly spaced, *except*
for the two values at either end of the vector. (Don't
ask me, I have no idea.) My "regularly spaced" interpolation
vector blows up on me at either end.

Cheers,

David

--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 13:14
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 11:49
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 09:54
		Re: GRIDDATA woes By: wgallery on Tue, 04 March 2008 09:43
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 09:14
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 09:05
		Re: GRIDDATA woes By: Brian Larsen on Tue, 04 March 2008 08:23
		Re: GRIDDATA woes By: ben.bighair on Tue, 04 March 2008 08:05
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 08:03
		Re: GRIDDATA woes By: David Fanning on Tue, 04 March 2008 07:35
		Re: GRIDDATA woes By: Kenneth P. Bowman on Mon, 03 March 2008 06:24
		Re: GRIDDATA woes By: wgallery on Mon, 03 March 2008 11:00
		Re: GRIDDATA woes By: Kenneth P. Bowman on Tue, 04 March 2008 19:04
		Re: GRIDDATA woes By: Kenneth P. Bowman on Tue, 04 March 2008 19:02
		Re: GRIDDATA woes By: wgallery on Tue, 04 March 2008 14:17
		Re: GRIDDATA woes By: Kenneth Bowman on Wed, 05 March 2008 06:14
		Re: GRIDDATA woes By: Kenneth P. Bowman on Tue, 04 March 2008 18:55
		Re: GRIDDATA woes By: ben.bighair on Tue, 04 March 2008 14:46
		Re: GRIDDATA woes By: pgrigis on Tue, 04 March 2008 14:39

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