R: Constructing a Legend Grob

legendGrob {grid}

R Documentation

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).

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)