Re: Generating Random Values with Do[]

*To*: mathgroup at smc.vnet.net*Subject*: [mg23300] Re: [mg23270] Generating Random Values with Do[]*From*: BobHanlon at aol.com*Date*: Sun, 30 Apr 2000 21:13:50 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Needs["Statistics`NormalDistribution`"] dist1 = NormalDistribution[0, 1]; dist2 = NormalDistribution[0, 1]; To reduce the memory requirements, break 10^6 trials into 100 sets of 10000 trials. nbrTrialsPerSet = 10000; nbrSets = 10^6/nbrTrialsPerSet; nbrRepeats = 3; Table[Plus @@ (Table[ Count[RandomArray[dist1, nbrTrialsPerSet] - RandomArray[dist2, nbrTrialsPerSet], _?NonNegative], {nbrSets}]), {nbrRepeats}] // Timing {149.26666666666665*Second, {500132, 499562, 499942}} In a message dated 4/29/2000 10:38:49 PM, com3 at ix.netcom*NOSPAM*.com writes: >I'm just at the beginning level of Mathematica programming and I need >to simulate a probabilistic process. I've constructed the code below >which (I believe) works fairly well. The intent is to compute the >number of times a randomly sampled value from distribution #1 will >equal or exceed a random sample from distribution #2 when a million >samples from each are compared. This is then repeated 3 times . I've >used ver. 3.0 for this. I have 3 questions though. > >1) How can I enhance this code such that I can easily change the >number of repeats, say from 3 to 10 without copying and pasting the >code ? Can this be done via an outer Do command ? > >2) Because a million samples from the two distributions are being >produced and compared, execution time is becoming an issue. Is there a >way I can speed up this code ? > >3) I understand that the random number generation seed is determined >from the system date. Could I be getting sub-quality random number >generation in my code ? In other words, do I need to worry about >"re-seeding" each time I call Random ? > >To get instant execution of the code, you can change the 10^6 to 10^2. > >Thanks in advance for any help suitable for the beginner. > Bob BobHanlon at aol.com