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Re: null array [message #36482 is a reply to message #36481]

Wed, 24 September 2003 01:33

Ben Panter
Messages: 102
Registered: July 2003

Senior Member

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!

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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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