plot.stepfun {stepfun}

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, 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"), ...)

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	numeric(2); range of x values to use.
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, f = 1)

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); plot(sfun1, xval=tt, add=TRUE, 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)
  plot(list(sfun0,sfun.2,sfun1)[[i]], add=TRUE, 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)

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