Message-ID: <176C97AAA877D24798ED7376652D0FD82757D4B19A@SRVEXCH02.epistem.local>
Date: 2013-03-15T09:31:58Z
From: elliott harrison
Subject: phyper returning zero
In-Reply-To: <CAAmySGO_-B5t=2NsUH4-Th+_5fvw=NjMxf555Z0NU5=j8=zkvg@mail.gmail.com>
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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