[R] Random Number Testing...
Prof Brian D Ripley
ripley at stats.ox.ac.uk
Sun Apr 8 10:33:18 CEST 2001
On Sun, 8 Apr 2001 Ko-Kang at xtra.co.nz wrote:
> Suppose I want to test a set of random numbers (using the Binormal random
> number generator), input the following command to generate a set of random
> test <- rbinom( 10000000, 1, 0.5 )
> How can I, after obtaining the result, export the vector "test" into an text
?write or see the R Data Import/Export manual. Do do this in smaller
pieces, though, using connections to keep the file open.
> Then, suppose I want to do something like:
> > x <- 1e10
> > x
>  1e+10
> > test <- rbinom( x, 1, 0.5 )
> Error in rbinom(n, size, prob) : invalid arguments
> Why would I get the error message given that x is a number?
Assuming you have a 32-bit machine, you can't allocate storage for 10
billion random numbers, and I think you also have an integer overflow
problem (10 billion is bigger than 2^32). In either case, n is invalid.
I don't get that error message but
> test <- rbinom( x, 1, 0.5 )
Error: cannot allocate vector of size 4194303 Kb
on Solaris. On i686 Linux I get what you reported. Probably asInteger
behaves differently, as it just takes (int) on a double, and I don't
think the behaviour of that when the double is out of range is prescribed
in the C standard.
Finally, if you could get 10billion numbers out, testing them is not really
fair as that's far more than one could reasonably use in an R simulation.
(Quick sanity check: they would take a week or so just to generate on a
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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