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Re: Another simple one [message #55061]

Mon, 30 July 2007 09:19

Jean H.
Messages: 472
Registered: July 2006

Senior Member

> Is that possible? Or does my array have to be square so have to
> truncate the whole thing at element 4 for example?
>
> Cheers,
>
> Snudge42
>

Hi,

You can also use a 1D array containing all of your data... then you
should know which entries correspond to which line...

ex: a = [1,2,3,4,5,6]

you can think of A as
1,2,3
,4,5
, ,6

So, but this starts to be useful with big arrays, you can have a 2D
array that indexes the 1D array...

ex:
indices2Dto1D = [[0,1,2],[-1,3,4],[-1,-1,5]]
print, "value of 2,2 = ", a[indices2Dto1D[2,2]] ==> 6
and
indices1Dto2D = [0,1,2,4,5,8]
print, "2D coords of the value 6 = ", indices1Dto2D[where(a eq 6)] ==>
8 (this is the 1D coordinate in the 2D array... you can transform it
back to 2,2)

Jean
PS: I use this all the time to keep satellite images covering a study
area having a crazy shape... I save about 75% of the otherwise required
memory! ... I have to keep only 1 array covering the entire area, and
all the other arrays cover only the study area!

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[Message index]

		Re: Another simple one By: Jean H. on Mon, 30 July 2007 09:19
		Re: Another simple one By: MarioIncandenza on Sun, 29 July 2007 12:39
		Re: Another simple one By: Brian Larsen on Sat, 28 July 2007 07:14
		Re: Another simple one By: Carsten Lechte on Sat, 28 July 2007 06:19
		Re: Another simple one By: Brian Larsen on Sat, 28 July 2007 05:45
		Re: Another simple one By: snudge42 on Wed, 08 August 2007 21:43

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