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Re: how can generate random integer numbers?
Posted:
Nov 17, 2005 6:18 PM


In article <h97ff.19781$tV6.15313@newssvr27.news.prodigy.net>, "Nasser Abbasi" <nma@12000.org> wrote:
> "emanuele" <emanuelemignosa@yahoo.it> wrote in message > news:ef1bf39.1@webx.raydaftYaTP... > > Hi all > > how can generate random integer numbers? > > Thanks in advantage Emanuele > > > First you need to decide on the range of random numbers. Then use > rand(1) to generate and floating random number between 0 and 1, then > map the generated number to the range you want, and then chop of the > fractional part. > > for example, if you want a random interger between 0 and 100, then > something like could be a solution > > >> round(rand(1)*100) > > ans = > > 48 > > if you want random intergers between 0 and 1000, then > > >> round(rand(1)*1000) > > etc.. > > if you want a random number between values other than 0 and some > positive upper limit, then you need to use a slightly more advanced > maping than the above. But the idea is the same. You use the random > number generated by rand(1) and map that to whatever you want. > > Nasser  Actually, in round(rand(1)*100), you wouldn't get a uniform distribution for all the integers from 0 to 100. The two end values, 0 and 100, would each have half the probability of occurring that other numbers in this range would have. You should use:
floor(101*rand) or ceil(101*rand1)
to get a uniform distribution. Each number would then have a probability of 1/101 of being chosen. Or in general, to get uniformly distributed integers in the range [m,n] (including the endpoints) use:
floor((nm+1)*rand+m) or ceil((nm+1)*rand+m1)
(Remove "xyzzy" and ".invalid" to send me email.) Roger Stafford



