plotCI: Plot Error Bars and Confidence Intervals

In gplots: Various R Programming Tools for Plotting Data

Plot Error Bars and Confidence Intervals

Description

Given a set of x and y values and interval width or upper and lower bounds, plot the points with error bars. This can be a useful tool for visualizing confidence intervals.

Usage

plotCI(x, y = NULL, uiw, liw = uiw, ui, li, err='y', ylim=NULL,
       xlim=NULL, type="p",  col=par("col"), barcol=col,
       pt.bg = par("bg"),  sfrac = 0.01, gap=1, lwd=par("lwd"),
       lty=par("lty"), labels=FALSE, add=FALSE, xlab, ylab,  minbar,
       maxbar, ... )

Arguments

x, y	coordinates for the center of error bars. y defaults to 1:n.
uiw	width of the upper or right error bar. Set to NULL or NA to omit upper bars.
liw	width of the lower or left error bar. Defaults to same value as uiw. Set to NULL or NA to omit lower bars.
ui	upper end of error bars. Defaults to y + uiw or x + uiw depeding on err. Set to NULL or NA to omit upper bars.
li	lower end of error bars. Defaults to y - liw or x - liw depedning on err. Set to NULL or NA to omit lower bars.
err	direction for error bars. Set to "y" for vertical bars. Set to "x" for horizontal bars. Defaults to "y".
col	color of plotting character used center marker of error bars. Default is "black".
xlim, ylim	range of x/y values to include in the plotting area.
type	point/line type; passed to points
barcol	color of the error bars. Defaults to the same value as col
pt.bg	background color of points (use pch=21, pt.bg=par("bg") to get open points superimposed on error bars).
sfrac	width of "crossbar" at the end of error bar as a fraction of the x plotting region. Defaults to 0.01.
gap	space left between the center of the error bar and the lines marking the error bar in units of the height (width) of the letter "O". Defaults to 1.0
lwd	width of bar lines.
lty	line type of bar lines.
labels	either a logical value indicating whether the circles representing the x values should be replaced with text giving the actual values or a vector containing labels to use instead. Defaults to FALSE.
add	logical indicating whether error bars should be added to the current plot. If FALSE (the defailt), a new plot will be created and symbols/labels for the x values will be plotted before drawing error bars.
minbar	minumum allowed value for bar ends. If specified, values smaller than minbar will be replaced with minbar.
maxbar	maximum allowed value for bar ends. If specified, values larger than maxbar will be replaced with maxbar.
...	optional plotting parameters
xlab	label for x axis.
ylab	label for y axis.

Author(s)

Original version by Bill Venables [e-mail] posted to r-help on Sep. 20, 1997. Enhanced version posted to r-help by Ben Bolker [e-mail] on Apr. 16, 2001. This version was modified and extended by Gregory R. Warnes [e-mail]. Additional changes suggested by Martin Maechler [e-mail] integrated on July 29, 2004.

See Also

plotmeans provides an enhanced wrapper to plotCI.

Examples

  # plot means and
  data(state)
  tmp   <- split(state.area, state.region)
  means <- sapply(tmp, mean)
  stdev <- sqrt(sapply(tmp, var))
  n     <- sapply(tmp,length)
  ciw   <- qt(0.975, n) * stdev / sqrt(n)

  # plain
  plotCI(x=means, uiw=ciw)

  # prettier
  plotCI(x=means, uiw=ciw, col="black", barcol="blue", lwd=1)

  # give mean values
  plotCI(x=means, uiw=ciw, col="black", barcol="blue",
         labels=round(means,-3), xaxt="n", xlim=c(0,5) )
  axis(side=1, at=1:4, labels=names(tmp), cex=0.7)

  # better yet, just use plotmeans ... #
  plotmeans( state.area ~ state.region )

gplots documentation built on Oct. 6, 2024, 1:07 a.m.