Help with Manipulate

*To*: mathgroup at smc.vnet.net*Subject*: [mg132002] Help with Manipulate*From*: "Eduardo M. A. M. Mendes" <emammendes at gmail.com>*Date*: Thu, 14 Nov 2013 02:11:44 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net

Hello I need to create a simple demonstration based upon an exercise on poisson counting processes. Here is the code Manipulate[n/Total[z],Style["Poisson Arrival Times",18,Bold],"",Delimiter,{{z,Flatten[{0,RandomVariate[Quiet@ExponentialDistribution[\[Lambda]],n-1]}]},Button["random",z=Flatten[{0,RandomVariate[Quiet@ExponentialDistribution[\[Lambda]],n-1]}]]&,Appearance->"Labeled"},"",Delimiter,{{\[Lambda],2,"\[Lambda]"},1,100,1,Appearance->"Labeled"},"",Delimiter,{{n,10000,"n"},1,1000000,1000,Appearance->"Labeled"},SaveDefinitions->True] The idea is to generate a sequence of random numbers, then take the sum of it and keep the last value. Every time I hit "random"a new sequence is created. The above code returns the following error msg RandomVariate::array : "\"The array dimensions -1 + n given in position 2 \ of RandomVariate[ExponentialDistribution[=CE=BB], -1 + n] should be a list of \ non-negative machine-sized integers giving the dimensions for the result. \"" and some weird output. After hitting "random", the output is what I expect but the whole Manipulate output is still red indicating that there are problems. Could you be so kind to point out what I did wrong and how to fix it? I feel that I did not quite get how Manipulate works. Many thanks Ed

**Follow-Ups**:**Re: Help with Manipulate***From:*Itai Seggev <itais@wolfram.com>

**Re: Help with Manipulate***From:*Tomas Garza <tgarza10@msn.com>

**Re: Help with Manipulate***From:*Waclaw Kusnierczyk <waku@idi.ntnu.no>