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Re: using the WHERE function on a portion of an array [message #59187 is a reply to message #59116]

Fri, 07 March 2008 09:05

becky_s
Messages: 4
Registered: February 2008

Junior Member

Jean,

Thanks for the tip about n_elements, I will do that! As for the other
stuff, I think we have the same idea but are talking at cross-
purposes. In your above example,
> ex: n_elements(A[*,0,0]) = 100 (10*10 array)
> index = 99 (last element of the 2D array)
> 99 * 100 = 9 900 ==> you are in the 99th plane, even if you haven't
> specified the plane!!!

My "indices" variable is actually from the 2D array A[0,*,*], but my
computation of the 1D index uses n_elements(A[*,0,0]). So, for
example, let A be a 4x2x2 array:
2830 0 0 0
2830 0 0 0

0 0 0 0
2830 0 0 0

and B another 4x2x2 array:
20 0 0 0
60 0 0 0

0 0 0 0
9 0 0 0

indices = WHERE(A[0,*,*] ge 2830 AND A[0,*,*] lt 2831, count)
;indices evaluates to 0, 1, 3

;Now, convert to 1D:
indices1D_B = indices * n_elements(A[*,0,0]) + 0
;yields 0, 4, 12

When I plug 0, 4, and 12 into B, I get the correct values I was
looking for,
B[0] = 20; B[4] = 60; B[12] = 9.

Hope that helps.
Becky

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[Message index]

		using the WHERE function on a portion of an array By: becky_s on Tue, 04 March 2008 11:23
		Re: using the WHERE function on a portion of an array By: Jean H. on Tue, 04 March 2008 15:20
		Re: using the WHERE function on a portion of an array By: becky_s on Fri, 07 March 2008 09:05

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