legendGrob Constructing a Legend Grob

Description

Constructing a legend grob (in progress)

Usage

legendGrob(labels, nrow, ncol, byrow = FALSE,
           do.lines = has.lty || has.lwd, lines.first = TRUE,
           hgap = unit(1, "lines"), vgap = unit(1, "lines"),
           default.units = "lines", pch, gp = gpar(), vp = NULL)

grid.legend(..., draw=TRUE)

Arguments

labels	legend labels (expressions)
nrow, ncol	integer; the number of rows or columns, respectively of the legend “layout”. nrow is optional and typically computed from the number of labels and ncol.
byrow	logical indicating whether rows of the legend are filled first.
do.lines	logical indicating whether legend lines are drawn.
lines.first	logical indicating whether legend lines are drawn first and hence in a plain “below” legend symbols.
hgap	horizontal space between the legend entries
vgap	vertical space between the legend entries
default.units	default units, see unit.
pch	legend symbol, numeric or character, passed to pointsGrob(); see also points for interpretation of the numeric codes.
gp	an R object of class "gpar", typically the output from a call to the function gpar, is basically a list of graphical parameter settings.
vp	a Grid viewport object (or NULL).
...	for grid.legend(): all the arguments above are passed to legendGrob().
draw	logical indicating whether graphics output should be produced.

Value

Both functions create a legend grob (a graphical object describing a plot legend), but only grid.legend draws it (only if draw is TRUE).

See Also

Grid, viewport; pointsGrob, linesGrob.

grid.plot.and.legend contains a simple example.

Examples

  ## Data:
  n <- 10
  x <- stats::runif(n) ; y1 <- stats::runif(n) ; y2 <- stats::runif(n)
  ## Construct the grobs :
  plot <- gTree(children=gList(rectGrob(),
                  pointsGrob(x, y1, pch=21, gp=gpar(col=2, fill="gray")),
                  pointsGrob(x, y2, pch=22, gp=gpar(col=3, fill="gray")),
                  xaxisGrob(),
                  yaxisGrob()))
  legd <- legendGrob(c("Girls", "Boys", "Other"), pch=21:23,
                     gp=gpar(col = 2:4, fill = "gray"))
  gg <- packGrob(packGrob(frameGrob(), plot),
                 legd, height=unit(1,"null"), side="right")

  ## Now draw it on a new device page:
  grid.newpage()
  pushViewport(viewport(width=0.8, height=0.8))
  grid.draw(gg)