lowess                 package:stats                 R Documentation

Scatter Plot Smoothing

Description:

     This function performs the computations for the _LOWESS_ smoother
     (see the reference below). 'lowess' returns a list containing
     components 'x' and 'y' which give the coordinates of the smooth.
     The smooth should be added to a plot of the original points with
     the function 'lines'.

Usage:

     lowess(x, y = NULL, f = 2/3, iter=3, delta = 0.01 * diff(range(xy$x[o])))

Arguments:

    x, y: vectors giving the coordinates of the points in the scatter
          plot. Alternatively a single plotting structure can be
          specified.

       f: the smoother span. This gives the proportion of points in the
          plot which influence the smooth at each value. Larger values
          give more smoothness.

    iter: the number of robustifying iterations which should be
          performed. Using smaller values of 'iter' will make 'lowess'
          run faster.

   delta: values of 'x' which lie within 'delta' of each other are
          replaced by a single value in the output from 'lowess'. 
          Defaults to 1/100th of the range of 'x'.

References:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

     Cleveland, W. S. (1979) Robust locally weighted regression and
     smoothing scatterplots. _J. Amer. Statist. Assoc._ *74*, 829-836.

     Cleveland, W. S. (1981) LOWESS: A program for smoothing
     scatterplots by robust locally weighted regression. _The American
     Statistician_, *35*, 54.

See Also:

     'loess'), a newer formula based version of 'lowess' (with
     different defaults!).

Examples:

     data(cars)
     plot(cars, main = "lowess(cars)")
     lines(lowess(cars), col = 2)
     lines(lowess(cars, f=.2), col = 3)
     legend(5, 120, c(paste("f = ", c("2/3", ".2"))), lty = 1, col = 2:3)

