[R] gam() in Splus and R

[Prof Brian Ripley]

On Sat, 18 Aug 2001, Ko-Kang Kevin Wang wrote:

> Hi,
>
> Is there any difference in the gam() function in R and Splus?

See Q7.18 in the FAQ!   They are quite different: in particular that in
R's mgcv does model selection and that in S-PLUS does not.

> I just tried to do an Ace Plot (plotting the result of the gam() ) on a
> dataset.  R gave me four (the data set has one response and four
> explanatory variables) ace plot with perfectly straight lines.  I kind of
> felt that it is highly unlikely, so I tried it in Splus.  Using the exact
> commands Splus gave me four completely different ace plots (in fact so
> different that three of them suggested a quadratic polynomial
> transformation).
>
> Am I doing something wrong here?

Something different, anyway.  mgcv's gam() can choose a linear model.

-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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