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
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