Random_number
in [Fortran]
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From: cubsfan on 11 Feb 2010 16:42 Hi, I've been working with astroparticle simulations using fortran, and I need to call random numbers. However, they need to be of a significant distance away from zero, in particular 2E16 or greater. Is there anyway to set a parameter with the 'random_number' command -- ie specify between what numbers the random one is generated? Thanks
From: Gus Gassmann on 11 Feb 2010 17:00 cubsfan wrote: > Hi, > > I've been working with astroparticle simulations using fortran, and I > need to call random numbers. However, they need to be of a > significant distance away from zero, in particular 2E16 or greater. > Is there anyway to set a parameter with the 'random_number' command -- > ie specify between what numbers the random one is generated? What else do you know about the distribution? It seems exceedingly unlikely that you'd have a uniform distribution under the circumstances. So you will need to use a transformation; the exact form will depend on the information you have about the random variable you want to model.
From: e p chandler on 11 Feb 2010 17:09 "cubsfan" <cubsfan334(a)gmail.com> wrote in message news:3195d648-18d7-442e-9f94-d4be74f94f25(a)q27g2000yqn.googlegroups.com... > Hi, > > I've been working with astroparticle simulations using fortran, and I > need to call random numbers. However, they need to be of a > significant distance away from zero, in particular 2E16 or greater. > Is there anyway to set a parameter with the 'random_number' command -- > ie specify between what numbers the random one is generated? > > Thanks random_number returns numbers uniformly distributed between zero and one (one excluded). It is easy enough to scale these to a uniform distribution over a particular range by linear interpolation. However you have not specified the probability model you are using for your random draws or what quantity you are simulating. --- e
From: Sjouke Burry on 11 Feb 2010 21:02 cubsfan wrote: > Hi, > > I've been working with astroparticle simulations using fortran, and I > need to call random numbers. However, they need to be of a > significant distance away from zero, in particular 2E16 or greater. > Is there anyway to set a parameter with the 'random_number' command -- > ie specify between what numbers the random one is generated? > > Thanks 2e16*(1+rand())
From: Richard Maine on 11 Feb 2010 21:14
Sjouke Burry <burrynulnulfour(a)ppllaanneett.nnll> wrote: > cubsfan wrote: > > > > I've been working with astroparticle simulations using fortran, and I > > need to call random numbers. However, they need to be of a > > significant distance away from zero, in particular 2E16 or greater. > > Is there anyway to set a parameter with the 'random_number' command -- > > ie specify between what numbers the random one is generated? > > > > Thanks > 2e16*(1+rand()) There is a standard Fortran random number intrinsic. Rand is not it. As the OP mentions, it is random_number. (Well, it isn't a "command", but that's a bit nitpicky). Since he already has that part right, I see no benefit in pointing him towards a nonportable, nonstandard form. I'd also second Gus's comment that one would need to have at least some further clue as to what kind of distribution was desired in order to give a good answer. -- Richard Maine | Good judgment comes from experience; email: last name at domain . net | experience comes from bad judgment. domain: summertriangle | -- Mark Twain |