[R] problems with loess

Prof Brian Ripley ripley at stats.ox.ac.uk
Fri Oct 7 18:14:58 CEST 2005

On Fri, 7 Oct 2005, Dimitri Giunchi wrote:

> Hi all,
> I was unable to obtained a smoothed line using the loess function.I used the following code reported in the examples of R documentation:
> cars.lo <- loess(dist ~ speed, cars)
> Then I tried to plot both the data and the smoothed line
> plot(cars)lines(cars.lo)
> but what I obtained is simply a broken line joining all the data points.I tried with different spans, but the results did not change.
> Does anyone know what's going wrong?

Yes. lines(cars.lo) plots the original data stored in the loess fit.

You need to predict, or use scatter.smooth to do it for you.

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

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