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Re: Subscripting multidimensional arrays [message #37284 is a reply to message #37278]

Fri, 12 December 2003 06:55

Chris Lee
Messages: 101
Registered: August 2003

Senior Member

In article <nwfCb.37807$SU2.20541@newssvr29.news.prodigy.com>, "Jonathan
Greenberg" <greenberg@ucdavis.edu> wrote:

> Hi all -- I was hoping to get some help with converting a vector which
> contains the x,y,z position for a value I want to exract from a
> multidimensional array -- I understand that using an array to subscript
> another array requires knowing the linear subscript position. For
> example: a = 0 10 20
> 30 40 50
> 60 70 80
>
> 90 100 110
> 120 130 140
> 150 160 170
> I have a vector which is defined as:
> locationvector=[2,2,2]
> I want to extract the value at that position (e.g. a[2,2,2] = 170), but
> I can't do a:
> a[locationvector] --> I apparently have to convert the locationvector to
> that linear position. How do I do this? Does IDL have a built in
> function that will do this conversion, or is there an easy formula for
> doing this conversion in ANY dimension? Thanks! --j
>

function element, array, loc_vector

s=size(array)
d=s[1:s[0]] ;dimensions
e=lonarr(s[0]) ;product of dimensions
e[0]=1L
for i=1L, s[0]-1 do e[i]=e[i-1]*d[i-1]
;e is the number of elements each dimension contains
return, total(loc_vector*e)

end

;;test
a=findgen(4,5,6)
;in this example, e=[1,4,20]

b=[2,3,4]
print, a[2,3,4], a[element(a,b)]
94.000 94.000

seems to work, there must be a better way though...

Chris.

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[Message index]

		Re: Subscripting multidimensional arrays By: JD Smith on Fri, 12 December 2003 13:35
		Re: Subscripting multidimensional arrays By: Chris Lee on Fri, 12 December 2003 13:15
		Re: Subscripting multidimensional arrays By: R.G. Stockwell on Fri, 12 December 2003 11:46
		Re: Subscripting multidimensional arrays By: R.G. Stockwell on Fri, 12 December 2003 11:44
		Re: Subscripting multidimensional arrays By: JD Smith on Fri, 12 December 2003 08:53
		Re: Subscripting multidimensional arrays By: R.G. Stockwell on Fri, 12 December 2003 08:57
		Re: Subscripting multidimensional arrays By: Chris Lee on Fri, 12 December 2003 06:55
		Re: Subscripting multidimensional arrays By: Jonathan Greenberg on Sat, 13 December 2003 12:19

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