sunflowerplot Produce a Sunflower Scatter Plot

Description

Multiple points are plotted as ‘sunflowers’ with multiple leaves (‘petals’) such that overplotting is visualized instead of accidental and invisible.

Usage

sunflowerplot(x, ...)

## Default S3 method:
sunflowerplot(x, y = NULL, number, log = "", digits = 6,
              xlab = NULL, ylab = NULL, xlim = NULL, ylim = NULL,
              add = FALSE, rotate = FALSE,
              pch = 16, cex = 0.8, cex.fact = 1.5,
              col = par("col"), bg = NA, size = 1/8, seg.col = 2,
              seg.lwd = 1.5, ...)

## S3 method for class 'formula'
sunflowerplot(formula, data = NULL, xlab = NULL, ylab = NULL, ...,
             subset, na.action = NULL)

Arguments

x	numeric vector of x-coordinates of length n, say, or another valid plotting structure, as for plot.default, see also xy.coords.
y	numeric vector of y-coordinates of length n.
number	integer vector of length n. number[i] = number of replicates for (x[i], y[i]), may be 0. Default (missing(number)): compute the exact multiplicity of the points x[], y[], via xyTable().
log	character indicating log coordinate scale, see plot.default.
digits	when number is computed (i.e., not specified), x and y are rounded to digits significant digits before multiplicities are computed.
xlab, ylab	character label for x-, or y-axis, respectively.
xlim, ylim	numeric(2) limiting the extents of the x-, or y-axis.
add	logical; should the plot be added on a previous one ? Default is FALSE.
rotate	logical; if TRUE, randomly rotate the sunflowers (preventing artefacts).
pch	plotting character to be used for points (number[i]==1) and center of sunflowers.
cex	numeric; character size expansion of center points (s. pch).
cex.fact	numeric shrinking factor to be used for the center points when there are flower leaves, i.e., cex / cex.fact is used for these.
col, bg	colors for the plot symbols, passed to plot.default.
size	of sunflower leaves in inches, 1[in] := 2.54[cm]. Default: 1/8\", approximately 3.2mm.
seg.col	color to be used for the segments which make the sunflowers leaves, see par(col=); col = "gold" reminds of real sunflowers.
seg.lwd	numeric; the line width for the leaves' segments.
...	further arguments to plot [if add = FALSE], or to be passed to or from another method.
formula	a formula, such as y ~ x.
data	a data.frame (or list) from which the variables in formula should be taken.
subset	an optional vector specifying a subset of observations to be used in the fitting process.
na.action	a function which indicates what should happen when the data contain NAs. The default is to ignore case with missing values.

Details

This is a generic function with default and formula methods.

For number[i] == 1, a (slightly enlarged) usual plotting symbol (pch) is drawn. For number[i] > 1, a small plotting symbol is drawn and number[i] equi-angular ‘rays’ emanate from it.

If rotate = TRUE and number[i] >= 2, a random direction is chosen (instead of the y-axis) for the first ray. The goal is to jitter the orientations of the sunflowers in order to prevent artefactual visual impressions.

Value

A list with three components of same length,

x	x coordinates
y	y coordinates
number	number

Use xyTable() (from package grDevices) if you are only interested in this return value.

Side Effects

A scatter plot is drawn with ‘sunflowers’ as symbols.

Author(s)

Andreas Ruckstuhl, Werner Stahel, Martin Maechler, Tim Hesterberg, 1989–1993. Port to R by Martin Maechler [email protected].

References

Chambers, J. M., Cleveland, W. S., Kleiner, B. and Tukey, P. A. (1983). Graphical Methods for Data Analysis. Wadsworth.

Schilling, M. F. and Watkins, A. E. (1994). A suggestion for sunflower plots. The American Statistician, 48, 303–305. doi: 10.2307/2684839.

Murrell, P. (2005). R Graphics. Chapman & Hall/CRC Press.

See Also

density, xyTable

Examples

require(stats) # for rnorm
require(grDevices)

## 'number' is computed automatically:
sunflowerplot(iris[, 3:4])
## Imitating Chambers et al, p.109, closely:
sunflowerplot(iris[, 3:4], cex = .2, cex.fact = 1, size = .035, seg.lwd = .8)
## or
sunflowerplot(Petal.Width ~ Petal.Length, data = iris,
              cex = .2, cex.fact = 1, size = .035, seg.lwd = .8)


sunflowerplot(x = sort(2*round(rnorm(100))), y = round(rnorm(100), 0),
              main = "Sunflower Plot of Rounded N(0,1)")
## Similarly using a "xyTable" argument:
xyT <- xyTable(x = sort(2*round(rnorm(100))), y = round(rnorm(100), 0),
               digits = 3)
utils::str(xyT, vec.len = 20)
sunflowerplot(xyT, main = "2nd Sunflower Plot of Rounded N(0,1)")

## A 'marked point process' {explicit 'number' argument}:
sunflowerplot(rnorm(100), rnorm(100), number = rpois(n = 100, lambda = 2),
              main = "Sunflower plot (marked point process)",
              rotate = TRUE, col = "blue4")