I would like to propose adding a new plot function to the 'graphics'
package. The new function is called areaplot() and I have implemented it
as a generic function that supports a variety of data classes.
An area plot consists of a simple line, like plot(x, y, type="l"),
except
the area between 0 and the line is a filled polygon. Areas can be stacked
on top of each other, like barplot(matrix(3:1)), and the data can be
plotted as proportions, so stacked areas equal 1.
Area plots are commonly found in the scientific literature. Currently,
drawing an area plot in R using polygon() is a hassle at best, and drawing
a stacked area plot can be a major task for beginning users.
If you source the attached areaplot.R file, and read the help page and
examples, you will see that I made an effort to implement the following
features:
- the same look as standard R plots, including default xlab and ylab
- the same graphical args as standard R plots, including add=TRUE
- the same robustness to NA values as standard R plots
- a generic function that supports vectors, tables, matrices, data frames,
lists, time-series objects, and formulas
On a technical note, I included the support for different data classes
inside areaplot.default(), instead of implementing separate areaplot.foo()
functions. It would be trivial to do move the if-clauses to separate
functions, but I wasn't sure if that would improve the code or not, since
the necessary data manipulations are minimal. It was only areaplot.formula
that should obviously be a separate function.
Comparable functions are found in some user packages, highlighting the
general need of an area plot function, but the existing functions do not
follow the R plotting standards, nor do they support such a variety of
data classes, or provide stacked and proportional area plots.
I'm looking forward to your feedback,
Arni
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areaplot <-
function(x, ...)
{
UseMethod("areaplot")
}
areaplot.default <-
function(x, y=NULL, prop=FALSE, add=FALSE, xlab=NULL, ylab=NULL, col=NULL, ...)
{
if(is.ts(x)) # ts/mts
{
if(is.null(ylab))
ylab <- deparse(substitute(x))
x <- data.frame(Time=time(x), x)
}
if(is.table(x)) # table
{
if(is.null(ylab))
ylab <- deparse(substitute(x))
if(length(dim(x)) == 1)
x <- t(t(unclass(x)))
else
x <- unclass(x)
}
if(is.matrix(x)) # matrix
{
if(!is.null(rownames(x)) &&
!any(is.na(suppressWarnings(as.numeric(rownames(x))))))
{
x <- data.frame(as.numeric(rownames(x)), x)
names(x)[1] <- ""
}
else
{
x <- data.frame(Index=seq_len(nrow(x)), x)
}
}
if(is.list(x)) # data.frame or list
{
if(is.null(xlab))
xlab <- names(x)[1]
if(is.null(ylab))
{
if(length(x) == 2)
ylab <- names(x)[2]
else
ylab <- ""
}
y <- x[-1]
x <- x[[1]]
}
if(is.null(y)) # one numeric vector passed, plot it on 1:n
{
if(is.null(xlab))
xlab <- "Index"
if(is.null(ylab))
ylab <- deparse(substitute(x))
y <- x
x <- seq_along(x)
}
if(is.null(xlab))
xlab <- deparse(substitute(x))
if(is.null(ylab))
ylab <- deparse(substitute(y))
y <- as.matrix(y)
if(is.null(col))
col <- gray.colors(ncol(y))
col <- rep(col, length.out=ncol(y))
if(prop)
y <- prop.table(y, 1)
y <- t(rbind(0, apply(y, 1, cumsum)))
na <- is.na(x) | apply(is.na(y),1,any)
x <- x[!na][order(x[!na])]
y <- y[!na,][order(x[!na]),]
if(!add)
suppressWarnings(matplot(x, y, type="n", xlab=xlab, ylab=ylab,
...))
xx <- c(x, rev(x))
for(i in 1:(ncol(y)-1))
{
yy <- c(y[,i+1], rev(y[,i]))
suppressWarnings(polygon(xx, yy, col=col[i], ...))
}
invisible(y[,-1])
}
areaplot.formula <-
function (formula, data, subset, na.action=NULL, ...)
{
m <- match.call(expand.dots=FALSE)
if(is.matrix(eval(m$data,parent.frame())))
m$data <- as.data.frame(data)
m$... <- NULL
m[[1]] <- as.name("model.frame")
if(as.character(formula[[2]]=="."))
{
rhs <- unlist(strsplit(deparse(formula[[3]])," *[:+] *"))
lhs <- sprintf("cbind(%s)",
paste(setdiff(names(data),rhs),collapse=","))
m[[2]][[2]] <- parse(text=lhs)[[1]]
}
mf <- eval(m, parent.frame())
if(is.matrix(mf[[1]]))
{
lhs <- as.data.frame(mf[[1]])
names(lhs) <- as.character(m[[2]][[2]])[-1]
areaplot.default(cbind(mf[-1],lhs), ...)
}
else
{
areaplot.default(mf[2:1], ...)
}
}
-------------- next part --------------
\name{areaplot}
\alias{areaplot}
\alias{areaplot.default}
\alias{areaplot.formula}
\title{Area Plots}
\description{
Produce a stacked area plot, or add polygons to an existing plot.
}
\usage{
areaplot(x, \dots)
\method{areaplot}{default}(x, y = NULL, prop = FALSE, add = FALSE, xlab = NULL,
ylab = NULL, col = NULL, \dots)
\method{areaplot}{formula}(formula, data, subset, na.action = NULL, \dots)
}
\arguments{
\item{x}{numeric vector of x values, or if \code{y=NULL} a numeric
vector of y values. Can also be a 1-dimensional table (x values in
names, y values in array), matrix or 2-dimensional table (x values
in row names and y values in columns), a data frame (x values in
first column and y values in subsequent columns), or a time-series
object of class \code{ts/mts}.}
\item{y}{numeric vector of y values, or a matrix containing y values
in columns.}
\item{prop}{whether data should be plotted as proportions, so stacked
areas equal 1.}
\item{add}{whether polygons should be added to an existing plot.}
\item{xlab}{label for x axis.}
\item{ylab}{label for y axis.}
\item{col}{fill color of polygon(s). The default is a vector of gray
colors.}
\item{formula}{a \code{\link{formula}}, such as \code{y ~ x} or
\code{cbind(y1, y2) ~ x}, specifying x and y values. A dot on the
left-hand side, \code{formula = . ~ x}, means all variables except
the one specified on the right-hand side.}
\item{data}{a data frame (or list) from which the variables in
\code{formula} should be taken.}
\item{subset}{an optional vector specifying a subset of observations
to be used.}
\item{na.action}{a function which indicates what should happen when
the data contain \code{NA} values. The default is to ignore missing
values in the given variables.}
\item{\dots}{further arguments passed to \code{matplot} and
\code{polygon}.}
}
\value{
Matrix of cumulative sums that was used for plotting.
}
\author{
Arni Magnusson.
}
\seealso{
\code{\link{barplot}}, \code{\link{polygon}}.
}
\examples{
areaplot(rpois(10,40))
areaplot(rnorm(10))
# formula
areaplot(Armed.Forces~Year, data=longley)
areaplot(cbind(Armed.Forces,Unemployed)~Year, data=longley)
# add=TRUE
plot(1940:1970, 500*runif(31), ylim=c(0,500))
areaplot(Armed.Forces~Year, data=longley, add=TRUE)
# matrix
areaplot(WorldPhones)
areaplot(WorldPhones, prop=TRUE)
# table
require(MASS)
areaplot(table(Aids2$age))
areaplot(table(Aids2$age, Aids2$sex))
# ts/mts
areaplot(austres)
areaplot(Seatbelts[,c("drivers","front","rear")],
ylab="Killed or seriously injured")
abline(v=1983+1/12, lty=3)
}
\keyword{kwd1}
\keyword{kwd2}
