lowess                 package:base                 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, f=2/3, iter=3, delta=.01*diff(range(x)))

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 replaced
          by a single value in the output from `lowess'.

References:

     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' (in package `modreg'), 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)

