French Curve

Median filtering aka "running medians" has one distinctive
advantage {over smooth.spline() or other so called linear smoothers}:
   It is "robust" i.e. not distorted by gross outliers.
Running medians is implemented in runmed() {standard "stats" package}
in a particularly optimized way rather than using the more general
running(.) approach of package 'gtools'.

Median smoothing splines are also implemented in the quantreg
package see ?rqss, but they produce piecewise linear fitting so
they may not appeal to those accustomed to french curves.


url:	www.econ.uiuc.edu/~roger        	Roger Koenker
email	rkoenker at uiuc.edu			Department of Economics
vox: 	217-333-4558				University of Illinois
fax:   	217-244-6678				Champaign, IL 61820