R: Plot Step Functions

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 = range(c(y, Fn.kn)),
         xlab = "x", ylab = "f(x)", main = NULL,
         add = FALSE, verticals = TRUE, do.points = (n < 1000),
         pch = par("pch"), col = par("col"),
         col.points = col, cex.points = par("cex"),
         col.hor = col, col.vert = 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` | limits for the plot region: see `plot.window`. Both have sensible defaults if omitted.
`xlab, ylab` | labels for 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. Default is true, for sample size < 1000.

`pch` | character; point character if `do.points`.
`col` | default color of all points and lines.
`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

    require(graphics)

    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.hor = "bisque")
    plot(sfun.2);plot(sfun.2, xval = tt, add = TRUE, col = "orange") # all colors
    plot(sfun1);lines(sfun1, xval = tt, col.hor = "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 = i)
    legend(2.5, 1.9, paste("f =", c(0, 0.2, 1)), col = 1:3, lty = 1, y.intersp = 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")

[Package stats version 3.1.2 Index]