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Re: Random selection [message #51245 is a reply to message #51243]

Sat, 11 November 2006 20:09

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article <MPG.1fbff8149c4b0217989db8@news.frii.com>,
David Fanning <news@dfanning.com> wrote:

> Jean H. writes:
>
>> What do you mean? that there is another method or that it can not return
>> more than once the same index? ... I would be interested in knowning
>> another method!!!
>>
>> IDL> a = (Round(Randomu(seed, 100) * 1000))

The problem with this approach is that it is actually rather likely
that you will generate two (or more) numbers that round to the
same 3-digit integer.

Sorting floats, on the other hand, involves no loss of precision.

If you really want to avoid duplicates, generate double-precision
random numbers

r = RANDOMU(seed, 1000, /DOUBLE)

Cheers, Ken

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[Message index]

		Re: Random selection By: greg michael on Sun, 12 November 2006 05:07
		Re: Random selection By: Julio[1] on Sun, 12 November 2006 04:57
		Re: Random selection By: Kenneth P. Bowman on Sat, 11 November 2006 20:09
		Re: Random selection By: David Fanning on Sat, 11 November 2006 14:09
		Re: Random selection By: Jean H. on Sat, 11 November 2006 13:25
		Re: Random selection By: David Fanning on Sat, 11 November 2006 13:08
		Re: Random selection By: Jean H. on Sat, 11 November 2006 12:45
		Re: Random selection By: David Fanning on Sat, 11 November 2006 05:30
		Re: Random selection By: greg michael on Sat, 11 November 2006 05:28
		Re: Random selection By: David Fanning on Sat, 11 November 2006 05:23
		Re: Random selection By: JD Smith on Mon, 13 November 2006 10:46

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