what you could (what I suggest) is not technically clean because your draw is not strictly random any more. But if you want to distribute 100 on 50 units with a Poisson-distributed variable x, then your lambda must be 100/50=2. You could then sample Poisson distribution ( rpois(50,2) ), sum over all 50 values and stop as soon as the sum is exactly 100. This may take a while though. And again, this is not strictly random as you are discarding lots of distributions to achieve that.
Cheers, Daniel ------------------------- cuncta stricte discussurus ------------------------- -----Ursprüngliche Nachricht----- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von Shubha Vishwanath Karanth Gesendet: Tuesday, July 08, 2008 2:54 AM An: [EMAIL PROTECTED]; [EMAIL PROTECTED] Betreff: Re: [R] Sum(Random Numbers)=100 ...actually I need to allocate certain amount of money (here I mentioned it as 100) to a randomly selected stocks(50 stocks)... i.e., 100 being divided among 50 stocks and preferably all are integer allocations(i.e., 5 8 56 12 etc without any decimals)... Thank you, Shubha -----Original Message----- From: Moshe Olshansky [mailto:[EMAIL PROTECTED] Sent: Tuesday, July 08, 2008 12:09 PM To: [EMAIL PROTECTED]; Shubha Vishwanath Karanth Subject: Re: [R] Sum(Random Numbers)=100 If they are really random you can not expect their sum to be 100. However, it is not difficult to get that given that the sum of n independent Poisson random variables equals N, any individual one has the conditional binomial distribution with size = N and p = 1/n, i.e. P(Xi=k/Sn=N) = (N over k)*(1/n)^k*((n-1)/n)^(N-k). So you can generate X1 binomial with size = 100 and p = 1/50; if X1 = k1 then the sum of the rest 49 must equal 100 - k1, so now you generate X2 binomial with size = 100-k1 and p = 1/49; if X2 = k2 then generate X3 binomial with size = 100 -(k1+k2) and p = 1/48, etc. Why do you need this? --- On Tue, 8/7/08, Shubha Vishwanath Karanth <[EMAIL PROTECTED]> wrote: > From: Shubha Vishwanath Karanth <[EMAIL PROTECTED]> > Subject: [R] Sum(Random Numbers)=100 > To: [EMAIL PROTECTED] > Received: Tuesday, 8 July, 2008, 3:58 PM Hi R, > > > > I need to generate 50 random numbers (preferably poisson), such that > their sum is equal to 100. How do I do this? > > > > > > Thank you, > > Shubha > > > > This e-mail may contain confidential and/or privileged > i...{{dropped:13}} > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. This e-mail may contain confidential and/or privileged i...{{dropped:10}} ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
