Re: Re: populate a list with random numbers fromnormal distribution?

*To*: mathgroup at smc.vnet.net*Subject*: [mg49989] Re: [mg49963] Re: [mg49855] populate a list with random numbers fromnormal distribution?*From*: Tomas Garza <tgarza01 at prodigy.net.mx>*Date*: Mon, 9 Aug 2004 04:29:30 -0400 (EDT)*References*: <200408070752.DAA07857@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The problem is, both the normal and the Poisson distributions have an infinite range (even if you may have a very small probability outside the 3 or 4 standard deviations away from the mean). Tomas ----- Original Message ----- From: "sean_incali" <sean_incali01 at yahoo.com> To: mathgroup at smc.vnet.net Subject: [mg49989] [mg49963] Re: [mg49855] populate a list with random numbers fromnormal distribution? > Hi. > > I hate it when i ask a question and not sound clear. I'm sure it's > frustrating for those who are really making efforts to help me out. > > let me try this. > > > --- Tomas Garza <tgarza01 at prodigy.net.mx> wrote: > > > Sean, > > Back to first principles: the normal distribution is a continuous > > distribution. Hence, a list of whatever integers can't possibly come > > from a > > normal distribution. > > > Right. I understand this now due to you and many others who tirelessly > pointed out my errors. (bless them all, lol) > > > >Sampling from a normal distribution will produce > > integers only with probability zero. You may, of course, define any > > distribution which will produce integers in the range you desire. > > E.g., a > > discrete uniform distribution which assigns probability 1/90000 to > > each > > integer in the range {10000,99999}, or any other distribution. > > Sampling from > > this distribution once and again will have a constant mean and > > variance. > > Yes this is kinda what i wanted. Only reason I wanted to use the > integers is because of the issues raised previously, and because i > didn't understand them fully. > > I wanted to pick the integers from a distribution in a range and then > scale the integers to make real numbers. > > You said the discrete uniform distribution will pick intergers in the > range {10000,99999}, or any other distribution. > > Will it do normal or poissonian distribution in that range? if so how > do I implement that? > > > > >Did > > I understand your problem correctly? > > > > I believe so. > > To add more information if it will help... > > I'm basically doing a perturbation analysis where i'm making random > perturbation to certain inputs into a system. and I woudl like to have > statistical information about the perturbation. (such as variance and > standard deviation and mean) > > then once I have perturbed the system, i would like to take an > output(s) and do the same statistical analysis to see what the system > did. > > which is why it was important to generate same variance and the mean > consistently because i will be performign this over and over. (if i > change the mean, std dev, and variance of inputs then the output will > be different also) > > I hope i have made my questions more understandable. > > thanks much in advance > > sean > > > Tomas > > ----- Original Message ----- > > From: "sean kim" <sean_incali at yahoo.com> To: mathgroup at smc.vnet.net > > To: "Tomas Garza" <tgarza01 at prodigy.net.mx> > > Cc: <mathgroup at smc.vnet.net> > > Sent: Thursday, August 05, 2004 12:15 AM > > Subject: [mg49989] [mg49963] Re: [mg49855] populate a list with random numbers > > fromnormaldistribution? > > > > > > > Hi tomas > > > > > > What I wanted to do is to pick sets of random Integers > > > in the ranges {10000, 99999} from the Normal > > > distribution such that, the mean is 50000 and the > > > standard deviation is 25000. > > > > > > or is that not normal distribution? will that be a > > > custom distribution? > > > > > > if that isn't possible, then I want to pick set of > > > random intgers ranging from {10000, 99999} such that > > > the variance and the mean and standard deviation do > > > not change across different runs. > > > > > > I think i'm supposed to use SeedRandom here but this > > > caused me problems also. > > > > > > so I need to design a routine that will pick random > > > integers in a given range with a given distribution > > > with the SAME mean, std dev/ and variances across > > > different runs or simulations. > > > > > > any insights will be truly appreciated. > > > > > > > > > sean > > > > > > > > > > > > > > l1 = Table[Random[NormalDistribution[50000,25000], > > > > Integer, {10000, 99999}], {1000}]; > > > > > > --- Tomas Garza <tgarza01 at prodigy.net.mx> wrote: > > > > > > > Check your syntax. Look at the following: > > > > > > > > In[1]:= > > > > << "Statistics`" > > > > > > > > In[2]:= > > > > dist = NormalDistribution[50000, 25000]; > > > > > > > > In[4]:= > > > > Table[Random[dist], {10}] > > > > Out[4]= > > > > {26975.950556122647, 58550.03432245862, > > > > 90456.47272543506, 73888.28476391576, > > > > 52046.50992913155, 72675.80052590193, > > > > 48593.27989475152, 78918.83089186646, > > > > 96303.52480806905, 69543.82643195332} > > > > > > > > What, then, do you mean by the variance of the above > > > > table? > > > > > > > > Tomas Garza > > > > Mexico City > > > > ----- Original Message ----- > > > > From: "sean kim" <sean_incali at yahoo.com> To: mathgroup at smc.vnet.net > To: mathgroup at smc.vnet.net > > > > To: <mathgroup at smc.vnet.net> > > > > Sent: Wednesday, August 04, 2004 9:46 AM > > > > Subject: [mg49989] [mg49963] [mg49855] populate a list with random > > > > numbers from normal > > > > distribution? > > > > > > > > > > > > > hello group. > > > > > > > > > > I looked at the help browser but i can't figure > > > > this out. I weant to > > > > > make a list of random numbers sampled from a > > > > normal distribution > > > > > > > > > > In[90]:= > > > > Needs["Statistics`ContinuousDistributions`"] > > > > > > > > > > l1 = Table[Random[NormalDistribution[50000,25000], > > > > Integer, {10000, > > > > > 99999}], {1000}]; > > > > > > > > > > Variance[l1]//N > > > > > StandardDeviation[l1]//N > > > > > > > > > > > > > > > From In[90]:= > > > > > Random::"randt": > > > > > Type specification NormalDistribution[50000, > > > > 25000] in > > > > > <<1>> should be Real, Integer, or Complex. > > > > > > > > > > Out[92]= > > > > > 0. > > > > > Out[93]= > > > > > 0. > > > > > > > > > > thanks in advance for any insights > > > > > > > > > > sean > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > __________________________________ > > > Do you Yahoo!? > > > Y! Messenger - Communicate in real time. Download now. > > > http://messenger.yahoo.com > > > > > > > > > > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Mail - 50x more storage than other providers! > http://promotions.yahoo.com/new_mail >

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