From: Javier Montoya on 12 Jun 2010 06:05 Dear all, I need to generate a vector of random float numbers between [0,1] such that their sum equals 1 and that are distributed nonuniformly. Is there any python function that generates such a vector? Best wishes
From: Etienne Rousee on 12 Jun 2010 07:08 Le 12/06/2010 12:05, Javier Montoya a �crit : > I need to generate a vector of random float numbers between [0,1] such > that their sum equals 1 and that are distributed nonuniformly. > Is there any python function that generates such a vector? Let f any function (injective is better). Let a1,...,an n numbers uniformly distributed. Let s the sum of f(a1),...,f(an). f(a1)/s, ... , f(an)/s is what you want. You have to choose f to obtain the distribution you prefer.  Etienne
From: Steven D'Aprano on 12 Jun 2010 08:09 On Sat, 12 Jun 2010 03:05:43 0700, Javier Montoya wrote: > Dear all, > > I need to generate a vector of random float numbers between [0,1] such > that their sum equals 1 and that are distributed nonuniformly. Is there > any python function that generates such a vector? You haven't explained your requirements in anywhere near enough detail. Any of these match your description: [1.0] [0.0, 0.0, 0.0, 0.0, 1.0] [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.3] [0.01, 0.01, 0.01, 0.01, 0.02, 0.02, 0.02, 0.03, 0.03, 0.84] and many, many more. What do you mean by "nonuniformly"? Do you have any specific distribution in mind? Do you have to have a particular number of items? For instance, you could do this: L = [] total = 0.0 while total < 1: x = random.uniform(0, 1total) L.append(x) total += x assert sum(L) == total == 1.0  Steven
From: Javier Montoya on 12 Jun 2010 08:27 On Jun 12, 1:08 pm, Etienne Rousee <etie...(a)rousee.org> wrote: > Le 12/06/2010 12:05, Javier Montoya a écrit : > > > I need to generate a vector of random float numbers between [0,1] such > > that their sum equals 1 and that are distributed nonuniformly. > > Is there any python function that generates such a vector? > > Let f any function (injective is better). > Let a1,...,an n numbers uniformly distributed. > Let s the sum of f(a1),...,f(an). > > f(a1)/s, ... , f(an)/s is what you want. > > You have to choose f to obtain the distribution you prefer. > >  > > Etienne Hi Etienne, Thanks for your suggestion. I ended with following code: N=5 a=np.random.random_integers(2*N, size=(1.,N)) a=a/float(sum(a)) However, in some cases, the random numbers are even repeated, for example, I obtained the following sequence: [0.03846154, 0.03846154, 0.23076923, 0.34615385, 0.34615385] This is mainly because in random_integers the integers generated might be repeated. One solution, would be to set the first parameter in random_integers to a larger number. What do you think? Do you suggest any other function instead of random_integers? Best wishes
From: Javier Montoya on 12 Jun 2010 08:27 On Jun 12, 1:08 pm, Etienne Rousee <etie...(a)rousee.org> wrote: > Le 12/06/2010 12:05, Javier Montoya a écrit : > > > I need to generate a vector of random float numbers between [0,1] such > > that their sum equals 1 and that are distributed nonuniformly. > > Is there any python function that generates such a vector? > > Let f any function (injective is better). > Let a1,...,an n numbers uniformly distributed. > Let s the sum of f(a1),...,f(an). > > f(a1)/s, ... , f(an)/s is what you want. > > You have to choose f to obtain the distribution you prefer. > >  > > Etienne Hi Etienne, Thanks for your suggestion. I ended with following code: N=5 a=np.random.random_integers(2*N, size=(1.,N)) a=a/float(sum(a)) However, in some cases, the random numbers are even repeated, for example, I obtained the following sequence: [0.03846154, 0.03846154, 0.23076923, 0.34615385, 0.34615385] This is mainly because in random_integers the integers generated might be repeated. One solution, would be to set the first parameter in random_integers to a larger number. What do you think? Do you suggest any other function instead of random_integers? Best wishes

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