> -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On Behalf Of Mike Miller > Sent: Sunday, April 29, 2012 5:21 PM > To: Vale Fara > Cc: r-help@r-project.org; billy am > Subject: Re: [R] generate random numbers for lotteries > > On Mon, 30 Apr 2012, Vale Fara wrote: > > > ok, what to do is to generate two sets (x,y) of integer uniform random > > numbers so that the following condition is satisfied: the sum of the > > numbers obtained in x,y matched two by two (first number obtained in x > > with first number obtained in y and so on) is in mean equal to a value > > z, mean value that I can decide before the randomization. > > > > Hope this is more clear than before... > > It isn't very clear to me. If you generate random X,Y pairs such that > (X+Y)/2=z, then you have a only one random number and a nother that is > completely dependent on it: > > X = random > Y = 2z - X. > > I'll just tell you one thing you might be able to use, but I don't have > time for this. > > To make a vector of N uniformly-distributed random integers in the range > from integer A to integer B, inclusive, you can do this: > > floor( runif(N, min=A, max=B+1) ) > > The floor() function rounds down to the nearest integer. Depending on the > exact nature of the algorithm, it might be possible for B+1 to happen, but > it would be extremely unlikely, if it really is possible. > > This should do the same thing: > > floor((B-A+1)*runif(N)+A) > > The ceiling function can accomplish the same thing. To make random > integers from 1 to K, do this: > > ceiling( K*runif(N) ) > > Mike >
I don't know what the OP is really trying to accomplish yet, and I am not motivated (yet) to try to figure it out. However, all this "flooring" and "ceiling) and "rounding" is not necessary for generating uniform random integers. For N integers in the range from A to B it is as simple as sample(A:B, N, replace=TRUE) Hope this is helpful, Dan Daniel Nordlund Bothell, WA USA ______________________________________________ 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.