From friendly at yorku.ca  Fri Jan 20 15:19:30 2012
From: friendly at yorku.ca (Michael Friendly)
Date: Fri, 20 Jan 2012 09:19:30 -0500
Subject: [Rd] nobs() and logLik()
In-Reply-To: <20120120144208.2d6fdfed@bossiaea>
References: <20120120133014.56c9fd05@bossiaea>
	<4F1907AE.3090302@stats.ox.ac.uk>
	<20120120144208.2d6fdfed@bossiaea>
Message-ID: <4F1977F2.8030905@yorku.ca>

On 1/20/2012 1:42 AM, Berwin A Turlach wrote:
> One reason that I can see for people to use zero weights rather than
> 'subset' is that fitted() and predict() in the former case readily
> produce fitted values for the observations that received a zero weight.
>
Another is that including the case of zero weights naturally allows a 
variety of simple robust methods via a weight function that descends to 
0.  A discontinuity at 0 in the handling of weights prevents this use.

-- 
Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street    Web:   http://www.datavis.ca
Toronto, ONT  M3J 1P3 CANADA



[Rd] nobs() and logLik()
Michael Friendly