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Re: newbie question on array manipulation [message #66285 is a reply to message #66283]

Tue, 05 May 2009 06:24

ben.bighair
Messages: 221
Registered: April 2007

Senior Member

On May 5, 7:53 am, "ben.bighair" <ben.bigh...@gmail.com> wrote:
> On May 5, 7:40 am, jpardila <blu...@gmail.com> wrote:
>
>> What is the best way to manipulate one array and remap its values
>> according to conditions?
>> Let's say I have a 2-d array, for all the elements equal to 5 I want
>> to change their values to 0. For values equal to 10 I want to convert
>> to 1 and so on. I am really confused and don't know if to use IF,
>> where, for or while. Thanks for answering this basic one.
>> JP
>
> Hi,
>
> The simplest is to use where - don't forget to use the output COUNT
> argument shown here as "na".
>
> a = WHERE(array EQ 10, na)
> if (na GT 0) then array[a] = 1
>
> If you are doing a multiple replacements (of different values) in a
> single array then you'll want to strap your sneakers on and use
> HISTOGRAM with it's REVERSE_INDICES output keyword. Seehttp://dfanning.com/tips/histogram_tutorial.htmlfor more on that - it
> is the swiss knife of IDL.
>

Hi again,

Another thought after a cup of coffee... if your application uses
floating point values instead of integers then you should search this
news group for info on how to test for equality with floats (single or
double precision).

Cheers (again),
Ben

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[Message index]

		Re: newbie question on array manipulation By: jpardila on Tue, 05 May 2009 23:54
		Re: newbie question on array manipulation By: ben.bighair on Tue, 05 May 2009 06:24
		Re: newbie question on array manipulation By: Jean H. on Tue, 05 May 2009 06:06
		Re: newbie question on array manipulation By: ben.bighair on Tue, 05 May 2009 04:53

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