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Re: WHERE - problem [message #33771]

Wed, 29 January 2003 09:31

Pavel A. Romashkin
Messages: 531
Registered: November 2000

Senior Member

Thomas Jordi wrote:
>
> thanks, it worked. however am I right, that the WHERE procedure is not
> able to handle the case, wehre you search values in a 3d array in one
> plane, and then want to acces with array[where] ?
>
> array(500,500,10)
> find=where(array(*,*,4) eq x)
>
> then the find-array with the subscripts indizes does not return the
> right values. it does it only at one or two dimensional arrays
> i thought, there must be a way like (array(find)) eg array(*,*,4(find))
> or whatever.
> So you cannot us the where for parts of the array only?

The deal here is, WHERE takes the explicitly specified dimension by
value, and analyzes the 2D array. If you look at the result of
WHERE(array[*, *, 4]) then you will see that the smallest index you can
get is 0, although you can't possibly want to use that zero and refer to
the entire Array. However, the following works:

find=where(array[*,*,4] eq x)
print, mean((array[*,*,4])[find])

or

s = size(array)
print, mean(array[find + 4*(s[1]*s[2])])

In the latter example, you do use Find to index Array, but you add the
size of the 3 ignored layers to Find, so the result is correct.
Hope this helps.
Cheers,
Pavel

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[Message index]

		Re: WHERE - problem By: Pavel A. Romashkin on Wed, 29 January 2003 09:31
		Re: WHERE - problem By: Thomas Jordi on Tue, 28 January 2003 22:10
		Re: WHERE - problem By: JD Smith on Tue, 28 January 2003 09:48

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