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Re: newbie: sub-array extraction [message #45813 is a reply to message #45808]

Thu, 13 October 2005 21:17

Dick Jackson
Messages: 347
Registered: August 1998

Senior Member

Hi Ben,

"Ben Rogers" <ben.jordanrogers@gmail.com> wrote in message
news:1129254169.767522.77270@g43g2000cwa.googlegroups.com...
> [...] I am looking to extract a 5x5 array around a central pixel to
> calculate some background statistics. Is this something best
> acomplished with for loops or is there an idl function that does
> something similar already?

Certainly. The section in Online Help that you might want is "subscripts",
but here's an example for you.

nX = 10
nY = 10
array = BIndGen(nX, nY)

pixX = 4
pixY = 6

subArray = array[pixX-2:pixX+2, pixY-2:pixY+2]
Print, subArray

... and I get:

42 43 44 45 46

52 53 54 55 56

62 63 64 65 66

72 73 74 75 76

82 83 84 85 86

To be more careful, truncating the array if the pixel[X|Y] is too close to
the edge:

pixX = 1
pixY = 9

subArray = array[(pixX-2)>0:(pixX+2)<(nX-1), (pixY-2)>0:(pixY+2)<(nY-1)]
Print, subArray

... and I get:

70 71 72 73

80 81 82 83

90 91 92 93

Hope this helps!

Cheers,
--
-Dick

Dick Jackson / dick@d-jackson.com
D-Jackson Software Consulting / http://www.d-jackson.com
Calgary, Alberta, Canada / +1-403-242-7398 / Fax: 241-7392

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[Message index]

		Re: newbie: sub-array extraction By: Ben Rogers on Sun, 16 October 2005 15:02
		Re: newbie: sub-array extraction By: Dick Jackson on Fri, 14 October 2005 09:20
		Re: newbie: sub-array extraction By: Dick Jackson on Thu, 13 October 2005 21:17
		Re: newbie: sub-array extraction By: gqshen2008@gmail.com on Wed, 19 October 2005 11:59

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