TeachingDemos (version 2.13)

panel.my.symbols: Draw Symbols (User Defined) on a Lattice Plot

Description

This function draws symbols on a lattice plot. It is similar to the builtin symbols function with the difference that it plots symbols defined by the user rather than a prespecified set of symbols.

Usage

panel.my.symbols(x, y, symb, inches=1, polygon=FALSE,
                       ..., symb.plots=FALSE, subscripts, MoreArgs)

Value

This function is run for its side effect of plotting, it returns an invisible NULL.

Arguments

x, y

The x and y coordinates for the position of the symbols to be plotted. These can be specified in any way which is accepted by xy.coords.

symb

Either a matrix, list, or function defining the symbol to be plotted. If it is a matrix or list it needs to be formatted that it can be passed directly to the llines function. It then defines the shape of the symbol on on a range/domain of -1 to 1. If this is a function it can either return a matrix or list as above (points on the range/domain of -1 to 1).

inches

The size of the square containing the symbol in inches (note: unlike symbols this cannot be FALSE).

polygon

If TRUE, use lpolygon function to plot rather than the llines function.

symb.plots

Currently not implemented.

...

Additional arguments will be replicated to the same length as x then passed to symb (if symb is a function) and/or the lines function (one value per symbol drawn).

subscripts

subscripts for the current panel

MoreArgs

A list with any additional arguments to be passed to the symb function (as is, without being replicated/split).

Author

Greg Snow

Details

The symb argument can be a 2 column matrix or a list with components 'x' and 'y' that defines points on the interval [-1,1] that will be connected with lines to draw the symbol. If you want a closed polygon then be sure to replicate the 1st point as the last point or use the polygon option.

If any point contains an NA then the line will not be drawn to or from that point. This can be used to create a symbol with disjoint parts that should not be connected.

If symb is a function then any unmatched arguments that end up in the '...' argument will be replicated to the same length as 'x' (using the rep function) then the values will be passed one at a time to the symb function. If MoreArgs is specified, the elements of it will also be passed to symb without modification. The symb function can either return a matrix or list with the points that will then be passed to the llines function (see above).

See Also

symbols, my.symbols, subplot, mapply, ms.polygram, lines

Examples

if(require(lattice)) {
  tmpdf <- data.frame( x=1:10, y=1:10, g=factor(rep( c("A","B"), each=5 )),
	z=c(1:5,5:1) )

  xyplot( y ~ x, tmpdf, panel=panel.my.symbols, symb=ms.female, inches=0.3 )

  xyplot( y ~ x | g, tmpdf, panel=panel.my.symbols, symb=ms.male, inches=0.3)

  xyplot( y ~ x, tmpdf, panel=panel.superpose, groups=g,
	panel.groups= function(group.number, ...) {
		if(group.number==1) {
			panel.my.symbols(..., symb=ms.male)
		} else {
			panel.my.symbols(..., symb=ms.female)
		} },
		inches=0.3
	)

  xyplot( y ~ x, tmpdf, panel=panel.my.symbols, symb=ms.polygram, n=tmpdf$z,
		inches=0.3)

  xyplot( y ~ x | g, tmpdf, panel=panel.my.symbols, symb=ms.polygram,
		n=tmpdf$z, inches=0.3)

  xyplot( y ~ x, tmpdf, panel=panel.superpose, groups=g,
	panel.groups = panel.my.symbols,
		inches=0.3, symb=ms.polygon, n=tmpdf$z, polygon=TRUE,
		adj=rep(c(0,pi/4),5)
	)
}