[R] Maxima/minima of loess line?

Jari Oksanen jarioksa at sun3.oulu.fi
Tue Aug 24 15:38:57 CEST 2004

On Tue, 2004-08-24 at 15:23, Liaw, Andy wrote:
> Just take range() of the fitted loess values.
Or if you really want to investigate the *line* instead of some random
*points*, you may need something like:

> optimize(function(x, mod) predict(mod, data.frame(speed=x)), c(0,20),
maximum=TRUE, mod=cars.lo)
[1] 19.99995
[1] 56.44498

This elaborates the ?loess example with the result object cars.lo (and,
of course is a bad example since the fit is monotone and solutions is
forced to the margin). Use maximum=FALSE for *a* minimum.

If you have several predictors, you either need to supply constant
values for those in optimize, or for simultaneous search in all use
optim or nlm.

cheers, jari oksanen
> > From: Fredrik Karlsson
> > 
> > Dear list,
> > 
> > I've produced a loess line that I would like to investigate 
> > in terms of 
> > local/global maxima and minima. How would you do this?
> > 
> > Thank you in advance.
> > 
> > /Fredrik Karlsson
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Jari Oksanen <jarioksa at sun3.oulu.fi>

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