Function to create a color key

Function to create a color key

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"
)