On Dec 15, 2011, at 1:35 PM, Alberto Magni wrote:
Hello everybody,
I have to compute something in this form:
x = prod(a:b) / prod(c:d), where: a < c and b < d and obviously: a
< b and c < d
I cannot make assumptions on the relative position of c,b and a,d.
The problem is that a,b,c,d are large and the products are huge (R
return Inf).
Well, R does have some limitations.
Their ratio is less than 1 but significantly higher than 0: it is a
non-tiny probability.
I need to find a way to simplify this ratio.
x <- exp( sum(log(a:b)) -sum(log(c:d)) )
The only way to solve this that I see is to decompose into prime
factors all the
numbers in the numerator and the denominator and to remove the ones
in common
Ewww. That does sound painful.
--
David Winsemius, MD
West Hartford, CT
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