From ripley at stats.ox.ac.uk  Fri Jun 29 08:03:32 2007
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Fri, 29 Jun 2007 07:03:32 +0100 (BST)
Subject: [Rd] inaccuracy in qbinom with partial argument matching
In-Reply-To: <468422A0.1040808@uni-bayreuth.de>
References: <468422A0.1040808@uni-bayreuth.de>
Message-ID: <Pine.LNX.4.64.0706290701540.30346@gannet.stats.ox.ac.uk>

On Thu, 28 Jun 2007, Peter Ruckdeschel wrote:

> Hi,
>
> I found the following strange effect with
> qbinom & partial argument matching
>
> p0 <- pbinom(0, size = 3, prob = 0.25)
> qbinom(p0,      size = 3, prob = 0.25)  ## 0 o.k.
> qbinom(p0-0.05, size = 3, prob = 0.25)  ## 0 o.k.
>
> ## positional matching:
> qbinom(p0,             3,        0.25)  ## 0 o.k.
>
> ## partial argument matching:
> qbinom(p0     , s = 3,    p    = 0.25)  ## 1 ???
> qbinom(p0-0.05, s = 3,    p    = 0.25)  ## 1 ???
> qbinom(p0-0.06, s = 3,    p    = 0.25)  ## 0 o.K.
>
> Unfortunately I have no I idea how to fix this.

You use a call that specifies your intentions accurately.  This is not 
'partial argument matching': 'p' is an exact match to the first argument 
of

> args(qbinom)
function (p, size, prob, lower.tail = TRUE, log.p = FALSE)

and that is how argument matching in R is documented to work.

The 'inaccuracy' is in the diagnosis: please see the FAQ.

-- 
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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595



[Rd] inaccuracy in qbinom with partial argument matching
Prof Brian Ripley