[R] phyper returning zero

[elliott harrison]

Thanks Michael I assumed as much but we know what that did.

Thanks again.

Elliott

-----Original Message-----
From: R. Michael Weylandt [mailto:michael.weylandt at gmail.com] 
Sent: 15 March 2013 09:29
To: elliott harrison
Cc: r-help at r-project.org
Subject: Re: [R] 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


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