| lowess {gplots} | R Documentation |
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.
lowess(x, ...)
## Default S3 method:
lowess(x, y = NULL, f = 2/3, iter = 3, delta = 0.01 *
diff(range(xy$x[o])), ...)
## S3 method for class 'formula':
lowess(formula,data = parent.frame(), subset, na.action,
f=2/3, iter=3, delta=.01*diff(range(mf[-response])), ... )
formula |
formula providing a single dependent variable (y) and an single independent variable (x) to use as coordinates in the scatter plot. |
data |
a data.frame (or list) from which the variables in `formula' should be taken. |
subset |
an optional vector specifying a subset of observations to be used in the fitting process. |
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. |
na.action |
a function which indicates what should happen when the data contain `NA's. The default is set by the `na.action' setting of `options', and is `na.fail' if that is unset. The ``factory-fresh'' default is `na.omit'. |
... |
parameters for methods. |
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.
loess (in package modreg), a newer
formula based version of lowess (with different defaults!).
data(cars)
# default method
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)
# formula method
plot(dist ~ speed, data=cars, main = "lowess(cars)")
lines(lowess(dist ~ speed, data=cars), col = 2)
lines(lowess(dist ~ speed, data=cars, f=.2), col = 3)
legend(5, 120, c(paste("f = ", c("2/3", ".2"))), lty = 1, col = 2:3)