| Re: array referencing problem ... [message #43045 is a reply to message #42954] |
Tue, 08 March 2005 16:02  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Andreas Brunn writes:
> I have a problem referencing a three dimensional array with a two
> dimensional mask. One solution I�m well aware of is building a two
> dimensional array and copy this in each channel of the three dimensional.
> But there must be a more elegant and memory saving method doing this, so i
> tried the following and ran in an in my eyes a little bit strange behaviour:
>
> ENVI> a=findgen(5,5,5)
> ENVI> ma=where(a le 10)
> ENVI> print, (a(*,*,1))(ma)
> 25.0000 26.0000 27.0000 28.0000 29.0000 30.0000 31.0000 32.0000 33.0000
> 34.0000 35.0000
> thats what I hoped and expected as a result
>
> but if I try the following:
> ENVI> (a(*,*,1))(ma) = 2
> % Expression must be named variable in this context: <FLOAT Array[5, 5]>.
> % Execution halted at: $MAIN$
>
> I only get that error message, where is my mistake ?
Too many parentheses. :-)
Here is an article that might help:
http://www.dfanning.com/code_tips/tempvar.html
> Is there a way applying this mask on each of the channels without copying
> each channel in a two dimensional array ?
I would have a look at the Dimensional Juggling Tutorial:
http://www.dfanning.com/tips/rebin_magic.html
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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