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Re: null array [message #36479 is a reply to message #36478]

Wed, 24 September 2003 08:11

R.Bauer
Messages: 1424
Registered: November 1998

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?
>
> I'll go back to my corner!
>
> Ben
>
> PS: Also, would it be possible to use the function temporary?
> a=temporary(a[1:*]) - would that be faster? I'm at home and not with my
> IDL so can't test it yet!
>

You are right,

Reimar

--
Reimar Bauer

Institut fuer Stratosphaerische Chemie (ICG-I)
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
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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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