symbols {graphics}

Draw Symbols (Circles, Squares, Stars, Thermometers, Boxplots)

Description

This function draws symbols on a plot. One of six symbols; circles, squares, rectangles, stars, thermometers, and boxplots, can be plotted at a specified set of x and y coordinates. Specific aspects of the symbols, such as relative size, can be customized by additional parameters.

Usage

symbols(x, y = NULL, circles, squares, rectangles, stars,
        thermometers, boxplots, inches = TRUE, add = FALSE,
        fg = par("col"), bg = NA,
        xlab = NULL, ylab = NULL, main = NULL,
        xlim = NULL, ylim = NULL, ...)

Arguments

x, y

the x and y co-ordinates for the centres of the symbols. They can be specified in any way which is accepted by xy.coords.

circles

a vector giving the radii of the circles.

squares

a vector giving the length of the sides of the squares.

rectangles

a matrix with two columns. The first column gives widths and the second the heights of rectangles.

stars

a matrix with three or more columns giving the lengths of the rays from the center of the stars. NA values are replaced by zeroes.

thermometers

a matrix with three or four columns. The first two columns give the width and height of the thermometer symbols. If there are three columns, the third is taken as a proportion: the thermometers are filled (using colour fg) from their base to this proportion of their height. If there are four columns, the third and fourth columns are taken as proportions and the thermometers are filled between these two proportions of their heights. The part of the box not filled in fg will be filled in the background colour (default transparent) given by bg.

boxplots

a matrix with five columns. The first two columns give the width and height of the boxes, the next two columns give the lengths of the lower and upper whiskers and the fifth the proportion (with a warning if not in [0,1]) of the way up the box that the median line is drawn.

inches

TRUE, FALSE or a positive number. See ‘Details’.

add

if add is TRUE, the symbols are added to an existing plot, otherwise a new plot is created.

fg

colour(s) the symbols are to be drawn in.

bg

if specified, the symbols are filled with colour(s), the vector bg being recycled to the number of symbols. The default is to leave the symbols unfilled.

xlab

the x label of the plot if add is not true. Defaults to the deparsed expression used for x.

ylab

the y label of the plot. Unused if add = TRUE.

main

a main title for the plot. Unused if add = TRUE.

xlim

numeric vector of length 2 giving the x limits for the plot. Unused if add = TRUE.

ylim

numeric vector of length 2 giving the y limits for the plot. Unused if add = TRUE.

...

graphics parameters can also be passed to this function, as can the plot aspect ratio asp (see plot.window).

Details

Observations which have missing coordinates or missing size parameters are not plotted. The exception to this is stars. In that case, the length of any ray which is NA is reset to zero.

Argument inches controls the sizes of the symbols. If TRUE (the default), the symbols are scaled so that the largest dimension of any symbol is one inch. If a positive number is given the symbols are scaled to make largest dimension this size in inches (so TRUE and 1 are equivalent). If inches is FALSE, the units are taken to be those of the appropriate axes. (For circles, squares and stars the units of the x axis are used. For boxplots, the lengths of the whiskers are regarded as dimensions alongside width and height when scaling by inches, and are otherwise interpreted in the units of the y axis.)

Circles of radius zero are plotted at radius one pixel (which is device-dependent). Circles of a very small non-zero radius may or may not be visible, and may be smaller than circles of radius zero. On windows devices circles are plotted at radius at least one pixel as some Windows versions omit smaller circles.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

W. S. Cleveland (1985) The Elements of Graphing Data. Monterey, California: Wadsworth.

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

See Also

stars for drawing stars with a bit more flexibility.

If you are thinking about doing ‘bubble plots’ by symbols(*, circles=*), you should really consider using sunflowerplot instead.

Examples

require(stats); require(grDevices)
x <- 1:10
y <- sort(10*runif(10))
z <- runif(10)
z3 <- cbind(z, 2*runif(10), runif(10))
symbols(x, y, thermometers = cbind(.5, 1, z), inches = .5, fg = 1:10)
symbols(x, y, thermometers = z3, inches = FALSE)
text(x, y, apply(format(round(z3, digits = 2)), 1, paste, collapse = ","),
     adj = c(-.2,0), cex = .75, col = "purple", xpd = NA)

## Note that  example(trees)  shows more sensible plots!
N <- nrow(trees)
with(trees, {
## Girth is diameter in inches
symbols(Height, Volume, circles = Girth/24, inches = FALSE,
        main = "Trees' Girth") # xlab and ylab automatically
## Colours too:
op <- palette(rainbow(N, end = 0.9))
symbols(Height, Volume, circles = Girth/16, inches = FALSE, bg = 1:N,
        fg = "gray30", main = "symbols(*, circles = Girth/16, bg = 1:N)")
palette(op)
})