R: Add Legends to Plots

legend {GMD} | R Documentation

## Add Legends to Plots

### Description

This function can be used to add legends to plots. Note that a call to the function `locator(1)` can be used in place of the `x` and `y` arguments.

### Usage

    legend(x, y = NULL, legend, fill = NULL, col = par("col"),
      border = "black", lty, lwd, pch, angle = 45, density = NULL,
      bty = "o", bg = par("bg"), box.lwd = par("lwd"), box.lty = par("lty"),
      box.col = par("fg"), pt.bg = NA, cex = 1, pt.cex = cex,
      pt.lwd = lwd, xjust = 0, yjust = 1, x.intersp = 1, y.intersp = 1,
      adj = c(0, 0.5), text.width = NULL, text.col = par("col"),
      merge = do.lines && has.pch, trace = FALSE, plot = TRUE, ncol = 1,
      horiz = FALSE, title = NULL, inset = 0, xpd, title.col = text.col,
      title.adj = 0.5, seg.len = 2)

### Arguments

`x` | the x coordinates to be used to position the legend.
`y` | the y coordinates to be used to position the legend. `x` and `y` can be specified by keyword or in any way which is accepted by `xy.coords`: See ‘Details’.
`legend` | a character or expression vector. of length >= 1 to appear in the legend. Other objects will be coerced by `as.graphicsAnnot`.
`fill` | if specified, this argument will cause boxes filled with the specified colors (or shaded in the specified colors) to appear beside the legend text.
`col` | the color of points or lines appearing in the legend.
`border` | the border color for the boxes (used only if `fill` is specified).
`lty` | the line types for lines appearing in the legend.
`lwd` | the line widths for lines appearing in the legend. One of `lty` and `lwd` must be specified for line drawing.
`pch` | the plotting symbols appearing in the legend, either as vector of 1-character strings, or one (multi character) string. Must be specified for symbol drawing.
`angle` | angle of shading lines.
`density` | the density of shading lines, if numeric and positive. If `NULL` or negative or `NA` color filling is assumed.
`bty` | the type of box to be drawn around the legend. The allowed values are `"o"` (the default) and `"n"`.
`bg` | the background color for the legend box. (Note that this is only used if `bty != "n"`.)
`box.lwd` | the line type for the legend box.
`box.lty` | the line width for the legend box.
`box.col` | the color for the legend box.
`pt.bg` | the background color for the `points`, corresponding to its argument `bg`.
`cex` | character expansion factor relative to current `par("cex")`.
`pt.cex` | expansion factor(s) for the points.
`pt.lwd` | line width for the points, defaults to the one for lines, or if that is not set, to `par("lwd")`.
`xjust` | how the legend is to be justified relative to the legend x location. A value of 0 means left justified, 0.5 means centered and 1 means right justified.
`yjust` | the same as `xjust` for the legend y location.
`x.intersp` | character interspacing factor for horizontal (x) spacing.
`y.intersp` | the same for vertical (y) line distances.
`adj` | numeric of length 1 or 2; the string adjustment for legend text. Useful for y-adjustment when `labels` are plotmath expressions.
`text.width` | the width of the legend text in x (`"user"`) coordinates. (Should be positive even for a reversed x axis.) Defaults to the proper value computed by `strwidth(legend)`.
`text.col` | the color used for the legend text.
`merge` | logical; if `TRUE`, merge points and lines but not filled boxes. Defaults to `TRUE` if there are points and lines.
`trace` | logical; if `TRUE`, shows how `legend` does all its magical computations.
`plot` | logical. If `FALSE`, nothing is plotted but the sizes are returned.
`ncol` | the number of columns in which to set the legend items (default is 1, a vertical legend).
`horiz` | logical; if `TRUE`, set the legend horizontally rather than vertically (specifying `horiz` overrides the `ncol` specification).
`title` | a character string or length-one expression giving a title to be placed at the top of the legend. Other objects will be coerced by `as.graphicsAnnot`.
`inset` | inset distance(s) from the margins as a fraction of the plot region when legend is placed by keyword.
`xpd` | if supplied, a value of the graphical parameter 'xpd' to be used while the legend is being drawn.
`title.col` | color for `title`.
`title.adj` | horizontal adjustment for `title`: see the help for `par("adj")`.
`seg.len` | the length of lines drawn to illustrate `lty` and/or `lwd` (in units of character widths).

### Details

see `legend` in package:graphics for details; Note: Old versions of graphics:::legend do not have ‘border’ option.

[Package GMD version 0.3.3 Index]