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Re: IDL removes dimensions of size 1 automatically [message #41190 is a reply to message #41189]

Fri, 24 September 2004 11:14

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Benjamin Hornberger wrote:
> Hi all,
>
> I had a hard time finding a bug which came from IDL's behaviour to
> remove dimensions of size 1 automatically sometimes.
>
> IDL> a=[[1u,1u]]
> IDL> help,a
> A UINT = Array[2]
> IDL> ;; IDL doesn't even let me specify this (2,1) element array
> IDL> a=reform(a,2,1)
> IDL> help,a
> A UINT = Array[2, 1]
> IDL> b=fix(a)
> IDL> help,b
> B INT = Array[2]
> IDL> ;; IDL removed my second dimension even though I just wanted to
> change the type
> IDL> c=2*a
> IDL> help,c
> C INT = Array[2]
> IDL> print,c
> 2 2
> IDL> ;; again IDL kicked out my second dimension
>
> I found this very annoying. Does anyone know more about it? Why is it
> like that? In which situations will IDL do that?

Only trailing dimensions of size 1 are removed.

IDL> x=fltarr(20,1,1,1,1)
IDL> help, x
X FLOAT = Array[20]
IDL> x=fltarr(1,1,1,1,20)
IDL> help, x
X FLOAT = Array[1, 1, 1, 1, 20]
IDL> x=fltarr(20,1,3,1,1)
IDL> help, x
X FLOAT = Array[20, 1, 3]

This has always been the case (in my experience) - much to the consternation of some IDL
users, and to the joy to others. YMMV.

paulv

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[Message index]

		Re: IDL removes dimensions of size 1 automatically By: Mark Hadfield on Wed, 29 September 2004 17:07
		Re: IDL removes dimensions of size 1 automatically By: David Fanning on Wed, 29 September 2004 11:46
		Re: IDL removes dimensions of size 1 automatically By: R.Bauer on Wed, 29 September 2004 08:01
		Re: IDL removes dimensions of size 1 automatically By: David Fanning on Mon, 27 September 2004 00:20
		Re: IDL removes dimensions of size 1 automatically By: Mark Hadfield on Sun, 26 September 2004 15:46
		Re: IDL removes dimensions of size 1 automatically By: R.Bauer on Sun, 26 September 2004 01:36
		Re: IDL removes dimensions of size 1 automatically By: btt on Fri, 24 September 2004 13:16
		Re: IDL removes dimensions of size 1 automatically By: Paul Van Delst[1] on Fri, 24 September 2004 11:14
		Re: IDL removes dimensions of size 1 automatically By: R.Bauer on Sun, 03 October 2004 00:14

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