Re: easy question about random numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg53413] Re: easy question about random numbers*From*: Mark Fisher <mark at markfisher.net>*Date*: Tue, 11 Jan 2005 01:30:44 -0500 (EST)*References*: <crqb7f$cak$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

With 5.1, we can use Piecewise as follows: MakeDiscreteRandomFunction[probs_] := MakeDiscreteRandomFunction[probs, Range[Length[probs]]] MakeDiscreteRandomFunction[probs_, vals_] := Block[{x}, Compile @@ {x, Piecewise @ Transpose[{vals, x <= # & /@ Rest@FoldList[Plus, 0, probs]}]} ] li2= {1/6, 1/6, 1/6, 1/6, 9/60, 11/60} ranfun = MakeDiscreteRandomFunction[li2] Usage: ranfun[Random[]] --Mark Pedrito wrote: > Hi everybody! > > I wanted to obtain a discrete random number generator that I needed for > a project. > > On the library Statistics`DiscreteDistributions` I could find the DiscreteUniformDistribution > function. But I wanted to specify the probability for each one of the > states. > > > For instance: > If we need to simulate an unfair dice, we could have this probabilities > for each one of the sides: > {1/6, 1/6, 1/6, 1/6, 9/60, 11/60} > > So I wrote: > li2 = {1/6, 1/6, 1/6, 1/6, 9/60, 11/60} > li3=FoldList[Plus,0,li2] > Module[{i = 1, r = Random[]}, While[ !li3[[i]] < r < li3[[i + 1]], i++]; i] > > It works ok but I don't know if there is another (better) way of doing > this. > Any suggestion? >