plot.stepfun {stats}R Documentation

Plot Step Functions

Description

Method of the generic plot for stepfun objects and utility for plotting piecewise constant functions.

Usage

## S3 method for class 'stepfun':
plot(x, xval, xlim, ylim,
     xlab = "x", ylab = "f(x)", main = NULL,
     add = FALSE, verticals = TRUE, do.points = TRUE,
     pch = par("pch"), col.points=par("col"), cex.points=par("cex"),
     col.hor = par("col"), col.vert= par("col"),
     lty = par("lty"), lwd = par("lwd"), ...)

## S3 method for class 'stepfun':
lines(x, ...)

Arguments

x an R object inheriting from "stepfun".
xval numeric vector of abscissa values at which to evaluate x. Defaults to knots(x) restricted to xlim.
xlim,ylim numeric(2) each; range of x or y values to use. Both have sensible defaults.
xlab,ylab labels of x and y axis.
main main title.
add logical; if TRUE only add to an existing plot.
verticals logical; if TRUE, draw vertical lines at steps.
do.points logical; if true, also draw points at the (xlim restricted) knot locations.
pch character; point character if do.points.
col.points character or integer code; color of points if do.points.
cex.points numeric; character expansion factor if do.points.
col.hor color of horizontal lines.
col.vert color of vertical lines.
lty, lwd line type and thickness for all lines.
... further arguments of plot(.), or if(add) segments(.).

Value

A list with two components

t abscissa (x) values, including the two outermost ones.
y y values ‘in between’ the t[].

Author(s)

Martin Maechler maechler@stat.math.ethz.ch, 1990, 1993; ported to R, 1997.

See Also

ecdf for empirical distribution functions as special step functions, approxfun and splinefun.

Examples

y0 <- c(1,2,4,3)
sfun0  <- stepfun(1:3, y0, f = 0)
sfun.2 <- stepfun(1:3, y0, f = .2)
sfun1  <- stepfun(1:3, y0, right = TRUE)

tt <- seq(0,3, by=0.1)
op <- par(mfrow=c(2,2))
plot(sfun0); plot(sfun0, xval=tt, add=TRUE, col.h="bisque")
plot(sfun.2);plot(sfun.2,xval=tt, add=TRUE, col.h="orange")
plot(sfun1);lines(sfun1, xval=tt, col.h="coral")
##-- This is  revealing :
plot(sfun0, verticals= FALSE,
     main = "stepfun(x, y0, f=f)  for f = 0, .2, 1")
for(i in 1:3)
  lines(list(sfun0,sfun.2,stepfun(1:3,y0,f = 1))[[i]], col.h=i, col.v=i)
legend(2.5, 1.9, paste("f =", c(0,0.2,1)), col=1:3, lty=1, y.inter=1); par(op)

# Extend and/or restrict 'viewport':
plot(sfun0, xlim = c(0,5), ylim = c(0, 3.5),
     main = "plot(stepfun(*), xlim= . , ylim = .)")

##-- this works too (automatic call to  ecdf(.)):
plot.stepfun(rt(50, df=3), col.vert = "gray20")
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