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MathGroup Archive 2004

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Re: shuffling (randomizing) a series

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52914] Re: [mg52857] shuffling (randomizing) a series
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Thu, 16 Dec 2004 03:41:52 -0500 (EST)
  • References: <200412150926.EAA10600@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

I suggest you use RandomPermutation in the AddOn 
DiscreteMath`Combinatorica`.

In[1]:=
<<DiscreteMath`Combinatorica`

Here you have a list of 1,000,000 integers:

In[2]:=
lstA = Table[Random[Integer, {1, 100}], {1000000}];

This will produce a random shuffling of the list in less than 5 seconds:

In[3]:=
AbsoluteTiming[lstA[[RandomPermutation[
     Length[lstA]]]]; ]
Out[3]=
{4.9687500 Second,Null}

Tomas Garza
Mexico City
----- Original Message ----- 
From: "George Szpiro" <george at netvision.net.il>
To: mathgroup at smc.vnet.net
Subject: [mg52914] [mg52857] shuffling (randomizing) a series


> Hello,
>
> I would like to put a series of numbers (of the order of 10^7 numbers) 
> into
> random order, i.e., to shuffle it. In Excel I would simply add a column 
> next
> to the column with the data, and then sort by the random number. But I 
> could
> only do this for 64000 numbers. How can I do that in Mathematica for a 
> file with a
> much larger series?
>
> (could you please copy any answer to my address:
> george at netvision.net.il)
>
> Thanks!
> George
>
>
> -- 
>
> --------
> George Szpiro
> Neue Zürcher Zeitung (Switzerland)
> POB 6278
> Jerusalem 91060
> Israel
>
>
>
>
> 



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