[Rd] LOESS (PR#9064)

[ripley at stats.ox.ac.uk]

On Fri, 7 Jul 2006, lamp at few.eur.nl wrote:

> Hello,
>
> I found a little BUG in loess <stats>. It does not receive the iterations
> parameter.

Please provide an example demonstrating this 'BUG', as we do ask you to 
do, along with basic information like your name, the version of R, the 
platform ....

> It can be debugged in the following way:

(Not in any sense of `debugged' that my dictionary mentions.)

> THIS IS AN EXCERPT FROM THE CODE:
>
> ....
>
> fit <- simpleLoess(y, x, w, span, degree, parametric, drop.square,
>        normalize, control$statistics, control$surface, control$cell,
>        iterations, control$trace.hat)
>
> Replace argument iterations with control$iterations.

Why?  The code contains a few lines earlier

     iterations <- if(family=="gaussian") 1 else control$iterations

which is the intention.  ?loess.control does say

iterations: the number of iterations used in robust fitting.
                                              ^^^^^^

> I found also remarkable differences when comparing loess with PROC LOESS
> (in SAS) using the same parameters and variables. It really confuses me.
> Where can I report this?

R-bugs is not a place to ask questions, but bugs in SAS can be reported to 
SAS inc.

-- 
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