

_P_l_o_t _S_t_e_p _F_u_n_c_t_i_o_n_s

     plot.stepfun(Fn, x, 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"), ...)

_A_r_g_u_m_e_n_t_s:

      Fn: an R object inheriting from `"stepfun"'.

       x: numeric vector of abscissa values at which to
          evaluate `Fn'.  Defaults to `knots(Fn)' restricted
          to `xlim'.

    xlim: numeric(2); range of `x' values to use.

     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.

xlab,ylab: labels of x and y axis.

    main: main title.

     ...: further arguments of `plot(.)', or if`(add)' `seg-
          ments(.)'.

_D_e_s_c_r_i_p_t_i_o_n:

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

_V_a_l_u_e:

     A list with two components

       t: abscissa (x) values, including the two outermost
          ones.

       y: y values `in between' the `t[]'.

_S_e_e _A_l_s_o:

     `ecdf' for empricial distribution functions as special
     step functions, `approxfun' and `splinefun'.

_E_x_a_m_p_l_e_s:

     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, x=tt, add=T, col.h="bisque")
     plot(sfun.2);plot(sfun.2,x=tt, add=T, col.h="orange")
     plot(sfun1); plot(sfun1, x=tt, add=T, 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")

