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Re: null array [message #36480 is a reply to message #36479]

Wed, 24 September 2003 06:52

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

Senior Member

Ben Panter wrote:
>
> Reimar Bauer wrote:
>> Tomson wrote:
>>
>>
>>> Hi, I need a null array without any elements in it. Then elements will be
>>> added to it. But how to define a null array?
>>>
>>> Best
>>> Tomsom
>>
>>
>> What is this? I don't use matlab.
>>
>> Would you like to do something like this.
>>
>> if n_elements(array) eq 0 then array=scalar else array=[array,scalar]
>>
>> Or in a loop
>>
>> for i=0,10 do begin
>> ..
>>
>> if i eq 0 then array=scalar else array=[array,scalar]
>> endfor
>
> I'm a bit worried about showing my ignorance here - but rather than have
> an 'if' running on every iteration, could you not do:
>
> a=[0.5]
>
> for i=0,n do begin
> ..
> endfor
>
> a=a[1:*]
>
> cutting out n if evaluations for the sake of 1 array crop?

Yep - I do that often. Not just in IDL either.

BTW, getting back to the original question, isn't every variable that hasn't yet been
defined in an IDL procedure (an infinite number to be sure) a null array? :o\

paulv

--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC

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[Message index]

		Re: null array By: David Fanning on Wed, 24 September 2003 18:35
		Re: null array By: tomson on Wed, 24 September 2003 17:47
		Re: null array By: JD Smith on Wed, 24 September 2003 09:17
		Re: null array By: R.Bauer on Wed, 24 September 2003 08:11
		Re: null array By: Paul Van Delst[1] on Wed, 24 September 2003 06:52
		Re: null array By: Ben Panter on Wed, 24 September 2003 02:08
		Re: null array By: Ben Panter on Wed, 24 September 2003 01:33
		Re: null array By: R.Bauer on Tue, 23 September 2003 20:21
		Re: null array By: David Fanning on Tue, 23 September 2003 20:04
		Re: null array By: David Fanning on Fri, 26 September 2003 02:24
		Re: null array By: Stein Vidar Hagfors H[2] on Tue, 30 September 2003 12:36

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