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Re: Satellite Swath Overlap [message #87527 is a reply to message #87523]

Wed, 12 February 2014 12:06

Phillip Bitzer
Messages: 223
Registered: June 2006

Senior Member

On Wednesday, February 12, 2014 11:14:21 AM UTC-6, Chase Calkins wrote:

>
> I was wanting to know if there is a way IDL can say where the overlap is and average the result between the two files in the overlap section.
>

Well, your example shows the arrays are the same size and cover the same lat/lon, so I would say they "overlap" everywhere (assuming the same thing as Andy about the size of result1/result2).

Let's say you have a missing value (again, building off Andy's example). The non-loop way would be to do something like this:

ind1 = WHERE(result1 EQ missingValue, count1) ;find missing values...
IF count1 NE 0 THEN result1[ind1] = !VALUES.F_NAN ;.. and replace them with NaNs

ind2 = WHERE(result2 EQ missingValue, count2) ;find/replace the missing value in result2 too...
IF count2 NE 0 THEN result2[ind2] = !VALUES.F_NAN

;to find the mean, build a 36x400x2 array, do the mean over the third dimension
resultAvg = MEAN([[[result1]], [[result2]]], dim=3, /NAN) ;avg the results

;find the NaNs; this will be where both arrays have the missing value...
indAvg = WHERE(~FINITE(resultAvg), countAvg)

IF countAvg NE 0 THEN resultAvg[indAvg] = missingValue ;...and put the missing value back

;go plot....

Notice I'm overwriting the original arrays - so you would modify this slightly if this isn't acceptable.

Also, I'm testing for equality between floats, always a precarious affair. You may want to test instead if the difference b/t the results and the missing value is some small number.

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[Message index]

		Satellite Swath Overlap By: Chase Calkins on Wed, 12 February 2014 09:14
		Re: Satellite Swath Overlap By: Andy Sayer on Wed, 12 February 2014 11:26
		Re: Satellite Swath Overlap By: Phillip Bitzer on Wed, 12 February 2014 12:06
		Re: Satellite Swath Overlap By: Chase Calkins on Wed, 12 February 2014 13:23

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