The R Project SVN R

% File src/library/graphics/man/spineplot.Rd

% Part of the R package, http://www.R-project.org

% Copyright 1995-2007 R Core Team

% Distributed under GPL 2 or later

\name{spineplot}

\alias{spineplot}

\alias{spineplot.default}

\alias{spineplot.formula}

\title{Spine Plots and Spinograms}

\description{

  Spine plots are a special cases of mosaic plots, and can be seen as

  a generalization of stacked (or highlighted) bar plots. Analogously,

  spinograms are an extension of histograms.

}

\usage{

spineplot(x, \dots)

\method{spineplot}{default}(x, y = NULL,

          breaks = NULL, tol.ylab = 0.05, off = NULL,

          ylevels = NULL, col = NULL,

          main = "", xlab = NULL, ylab = NULL,

          xaxlabels = NULL, yaxlabels = NULL,

          xlim = NULL, ylim = c(0, 1), axes = TRUE, \dots)

\method{spineplot}{formula}(formula, data = NULL,

          breaks = NULL, tol.ylab = 0.05, off = NULL,

          ylevels = NULL, col = NULL,

          main = "", xlab = NULL, ylab = NULL,

          xaxlabels = NULL, yaxlabels = NULL,

          xlim = NULL, ylim = c(0, 1), axes = TRUE, \dots,

          subset = NULL)

}

\arguments{

  \item{x}{an object, the default method expects either a single variable

    (interpreted to be the explanatory variable) or a 2-way table.  See

    details.}

  \item{y}{a \code{"factor"} interpreted to be the dependent variable}

  \item{formula}{a \code{"formula"} of type \code{y ~ x} with a single

    dependent \code{"factor"} and a single explanatory variable.}

  \item{data}{an optional data frame.}

  \item{breaks}{if the explanatory variable is numeric, this controls how

    it is discretized. \code{breaks} is passed to \code{\link{hist}} and can

    be a list of arguments.}

  \item{tol.ylab}{convenience tolerance parameter for y-axis annotation.

    If the distance between two labels drops under this threshold, they are

    plotted equidistantly.}

  \item{off}{vertical offset between the bars (in per cent). It is fixed to

    \code{0} for spinograms and defaults to \code{2} for spine plots.}

  \item{ylevels}{a character or numeric vector specifying in which order

    the levels of the dependent variable should be plotted.}

  \item{col}{a vector of fill colors of the same length as \code{levels(y)}.

    The default is to call \code{\link{gray.colors}}.}

  \item{main, xlab, ylab}{character strings for annotation}

  \item{xaxlabels, yaxlabels}{character vectors for annotation of x and y axis.

    Default to \code{levels(y)} and \code{levels(x)}, respectively for the

    spine plot. For \code{xaxlabels} in the spinogram, the breaks are

    used.}

  \item{xlim, ylim}{the range of x and y values with sensible defaults.}

  \item{axes}{logical.  If \code{FALSE} all axes (including those giving

    level names) are suppressed.}

  \item{\dots}{additional arguments passed to \code{\link{rect}}.}

  \item{subset}{an optional vector specifying a subset of observations

    to be used for plotting.  }

}

\details{

  \code{spineplot} creates either a spinogram or a spine plot.  It can

  be called via \code{spineplot(x, y)} or \code{spineplot(y ~ x)} where

  \code{y} is interpreted to be the dependent variable (and has to be

  categorical) and \code{x} the explanatory variable.  \code{x} can be

  either categorical (then a spine plot is created) or numerical (then a

  spinogram is plotted).  Additionally, \code{spineplot} can also be

  called with only a single argument which then has to be a 2-way table,

  interpreted to correspond to \code{table(x, y)}.

  Both, spine plots and spinograms, are essentially mosaic plots with

  special formatting of spacing and shading.  Conceptually, they plot

  \eqn{P(y | x)} against \eqn{P(x)}.  For the spine plot (where both

  \eqn{x} and \eqn{y} are categorical), both quantities are approximated

  by the corresponding empirical relative frequencies.  For the

  spinogram (where \eqn{x} is numerical), \eqn{x} is first discretized

  (by calling \code{\link{hist}} with \code{breaks} argument) and then

  empirical relative frequencies are taken.

  Thus, spine plots can also be seen as a generalization of stacked bar

  plots where not the heights but the widths of the bars corresponds to

  the relative frequencies of \code{x}. The heights of the bars then

  correspond to the conditional relative frequencies of \code{y} in

  every \code{x} group. Analogously, spinograms extend stacked

  histograms.

}

\value{

  The table visualized is returned invisibly.

}

\seealso{

  \code{\link{mosaicplot}}, \code{\link{hist}}, \code{\link{cdplot}}

}

\references{

  Friendly, M. (1994), Mosaic displays for multi-way contingency tables.

  \emph{Journal of the American Statistical Association}, \bold{89},

  190--200.

  Hartigan, J.A., and Kleiner, B. (1984), A mosaic of television ratings.

  \emph{The American Statistician}, \bold{38}, 32--35.

  Hofmann, H., Theus, M. (2005), \emph{Interactive graphics for visualizing

  conditional distributions}, Unpublished Manuscript.

  Hummel, J. (1996), Linked bar charts: Analysing categorical data graphically.

  \emph{Computational Statistics}, \bold{11}, 23--33.

}

\author{

  Achim Zeileis \email{Achim.Zeileis@R-project.org}

}

\examples{

## treatment and improvement of patients with rheumatoid arthritis

treatment <- factor(rep(c(1, 2), c(43, 41)), levels = c(1, 2),

                    labels = c("placebo", "treated"))

improved <- factor(rep(c(1, 2, 3, 1, 2, 3), c(29, 7, 7, 13, 7, 21)),

                   levels = c(1, 2, 3),

                   labels = c("none", "some", "marked"))

## (dependence on a categorical variable)

(spineplot(improved ~ treatment))

## applications and admissions by department at UC Berkeley

## (two-way tables)

(spineplot(margin.table(UCBAdmissions, c(3, 2)),

           main = "Applications at UCB"))

(spineplot(margin.table(UCBAdmissions, c(3, 1)),

           main = "Admissions at UCB"))

## NASA space shuttle o-ring failures

fail <- factor(c(2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1,

                 1, 1, 1, 2, 1, 1, 1, 1, 1),

               levels = c(1, 2), labels = c("no", "yes"))

temperature <- c(53, 57, 58, 63, 66, 67, 67, 67, 68, 69, 70, 70,

                 70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81)

## (dependence on a numerical variable)

(spineplot(fail ~ temperature))

(spineplot(fail ~ temperature, breaks = 3))

(spineplot(fail ~ temperature, breaks = quantile(temperature)))

## highlighting for failures

spineplot(fail ~ temperature, ylevels = 2:1)

}

\keyword{hplot}