| Re: Random ordering [message #35528] |
Tue, 24 June 2003 13:55 |
James Kuyper
Messages: 425
Registered: March 2000
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Senior Member |
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David Fanning wrote:
>
> trouble writes:
>
>> Stuck again. I want to create an integer 1D array from 0 to n (n ~
>> 100) so that the numbers are in jumbled up order so that "nearby"
>> numbers, eg. ABS(difference) < 3, are "far" apart. I think there must
>> be a nice way using MOD rather than bludging it with RANDOMU. Anyone
>> got any suggestions?
Any algorithm than uses MOD rather than RANDOMU must necessarily be
non-random, so I'm assuming a completely regular result is acceptable?
By "jumbled up" do you mean a permutation of indgen(n), as opposed to a
sequence that might contain repeats?
If so, then try
jumble = (jumble_increment(n,m)*INDGEN(n)) MOD n
for m=3, which is the limit you've placed on ABS(difference).
jumble_increment(n,m) is the integer between 0 and n which is nearest to
n/m, which does NOT divide 'n'. The algorithm for jumble_increment() is
left as an excersize for the reader (I'm being lazy).
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| Re: Random ordering [message #35529 is a reply to message #35528] |
Tue, 24 June 2003 13:14  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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trouble writes:
> Stuck again. I want to create an integer 1D array from 0 to n (n ~
> 100) so that the numbers are in jumbled up order so that "nearby"
> numbers, eg. ABS(difference) < 3, are "far" apart. I think there must
> be a nice way using MOD rather than bludging it with RANDOMU. Anyone
> got any suggestions?
What is you do, anyway, for a living, Trouble?
Cheers,
David
--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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