Function to create a color key

Usage

colorkey(
  x0,
  y0,
  x1,
  y1,
  cols = c("white", "steelblue"),
  tick.range = c(0, 1),
  tick.marks = seq(tick.range[1], tick.range[2], length.out = 5L),
  label.from = NULL,
  label.to = NULL,
  nlevels = 100,
  main = NULL,
  relative = TRUE,
  tick.args = list(),
  label.args = list(),
  main.args = list()
)

Arguments

x0, x1, y0, y1: Numeric scalars. Coordinates of the lower left and upper right points where the color key will be drawn as proportion of the plotting region.
cols: Character scalar. Colors specifications to create the color palette.
tick.range, tick.marks: Numeric vectors specifying the range and the tickmarks respectively.
label.from, label.to: Character scalar. Labels of the lower and upper values of the color key.
nlevels: Integer scalar. Number of levels to extrapolate.
main: Character scalar. Title of the colorkey.
relative: Logical scalar. When TRUE the color key is drawn relative to the plotting region area taking x0, x1, y0, y1 as relative location.
tick.args, label.args, main.args: Lists of arguments passed to graphics::text for drawing ticks, labels and main respectively.

Value

NULL.

Examples

set.seed(22231)

# A random figure
dat <- matrix(runif(100*3), ncol = 3)
col <- colorRamp2(c("blue", "white", "red"))

plot(
  dat[,1], dat[,2],
  col = rgb(col(dat[,3]), maxColorValue=255),
  cex=2, pch=20
  )

# Pretty color key
colorkey(
  x0 = .60, y0 = .80,
  x1 = .95, y1 = .95,
  cols = c("blue", "white", "red"),
  main = "Some color scale"
)