Re: need help

• To: mathgroup at smc.vnet.net
• Subject: [mg87357] Re: need help
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Tue, 8 Apr 2008 07:15:53 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <ftcoug\$ksr\$1@smc.vnet.net>

```haitomi wrote:

> I need help with two pure functions
>
> 1)  Li[Ranlist,x] that return a list of x element selected at random from Ranlist.  (Is there any way to gennerate random from Ranlist? For example I have RanList=Range[-100,100])

<snip>

Hi Tomi,

I am not sure to have understood what you are looking for, but I hope
the following will help.

First, note that if one wants to get a list of, say ten, integers within
the range [-100, 100], one can use RandomInteger as in

RandomInteger[{-100, 100}, 10]

{-60, -36, -40, -45, 6, 26, -84, 2, -45, 77}

There exists some other functions such as RandomReal or RandomComplex
too. If one wants to randomly pick out some symbols, one can use

RandomChoice[{a, b, c}, 10]

{c, a, b, b, c, c, c, b, b, c}

Now if you prefer to write your own function, you could use something
like the following:

f1[lst_, n_?NonNegative] /; n <= Length[lst] :=
lst[[RandomInteger[{1, Length[lst]}, n]]]

RanList = Range[-10, 10]

{-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9,10}

(* We randomly pick out five integer values out of twenty. *)

f1[RanList, 5]

{-3, 7, -3, 9, 1}

Regards,
-- Jean-Marc

```

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