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Re: Random function [message #180548 is a reply to message #180546]

Mon, 25 February 2013 21:42

Jerry Stuckle
Messages: 2598
Registered: September 2010

Karma:

Senior Member

On 2/25/2013 4:13 PM, Luuk wrote:
> On 25-02-2013 21:57, Salvatore wrote:
>> On 2013-02-25, sonnichjensen(at)gmail(dot)com <sonnichjensen(at)gmail(dot)com> wrote:
>>> Hi
>>>
>>> I use the rand function to get 10 items of 1808 current itemes. I
>>> tried some 50 times or so and I can clearly see that it has a few
>>> "faivourite numbers" which comes all the time, and some whihc I still
>>> have to see (I am talking about large groups of items from the 1808
>>> picture, that I still have to see)
>>>
>>> How I can get a better random function?
>>
>> Try mt_rand().
>>
>
>
> file: rand.php
> <?php
> for ($x=1; $x<=180800; $x++) {
> echo mt_rand(1,1808)."\n";
> }
> ?>
>
> bash:
> $ php -f rand.php | sort | uniq -c | awk 'BEGIN {m=9999; r=0; }{ if
> ($1<m) { m=$1; }; if ($1>r) { r=$1; }} END{ print m,r; }'
> 72 134
>
> This means that some number only was picked 72 times,
> and another number was picked 134 times......
>
>

That's pretty much within statistical variance. Remember, it does NOT
mean you'll get an even distribution - in fact if you did, by definition
the results wouldn't be random.

The key is - what happens if you do it multiple times? Does the same
number show a similar pattern?

--
==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================

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[Message index]

		Random function By: Sonnich Jensen on Mon, 25 February 2013 20:48
		Re: Random function By: Salvatore on Mon, 25 February 2013 20:57
		Re: Random function By: Luuk on Mon, 25 February 2013 21:13
		Re: Random function By: Jerry Stuckle on Mon, 25 February 2013 21:42
		Re: Random function By: The Natural Philosoph on Mon, 25 February 2013 22:12
		Re: Random function By: Robert Heller on Tue, 26 February 2013 01:46
		Re: Random function By: Jerry Stuckle on Mon, 25 February 2013 21:39
		Re: Random function By: The Natural Philosoph on Mon, 25 February 2013 22:11
		Re: Random function By: Salvatore on Mon, 25 February 2013 22:42
		Re: Random function By: M. Strobel on Tue, 26 February 2013 10:18
		Re: Random function By: Paul Herber on Tue, 26 February 2013 13:52
		Re: Random function By: Markus Grob on Wed, 27 February 2013 11:17
		Re: Random function By: Thomas 'PointedEars' on Wed, 27 February 2013 23:22

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