phyper returning zero
On Fri, Mar 15, 2013 at 8:52 AM, elliott harrison
<e.harrison at epistem.co.uk> wrote:
Hi, I am attempting to use phyper to test the significance of two overlapping lists. I keep getting a zero and wondered if that was determining non-significance of my overlap or a p-value too small to calculate? overlap = 524 lista = 2784 totalpop = 54675 listb = 1296 phyper(overlap, lista, totalpop, listb,lower.tail = FALSE, log.p=F) [1] 0
If you set log.p = T, you see that the _log_ of the desired value is -800, so it's likely simply too small to fit in a IEEE double. In sort, for all and any practical purposes, your p-value is zero. Cheers, MW