Sequential grey colour scales

Source: R/scale-grey.r, R/zxx.r

Based on gray.colors(). This is black and white equivalent of scale_colour_gradient().

scale_colour_grey(..., start = 0.2, end = 0.8, na.value = "red",
  aesthetics = "colour")

scale_fill_grey(..., start = 0.2, end = 0.8, na.value = "red",
  aesthetics = "fill")

Arguments

...

Arguments passed on to discrete_scale

palette

A palette function that when called with a single integer argument (the number of levels in the scale) returns the values that they should take.

breaks

One of:

  • NULL for no breaks

  • waiver() for the default breaks computed by the transformation object

  • A character vector of breaks

  • A function that takes the limits as input and returns breaks as output

limits

A character vector that defines possible values of the scale and their order.

drop

Should unused factor levels be omitted from the scale? The default, TRUE, uses the levels that appear in the data; FALSE uses all the levels in the factor.

na.translate

Unlike continuous scales, discrete scales can easily show missing values, and do so by default. If you want to remove missing values from a discrete scale, specify na.translate = FALSE.

na.value

If na.translate = TRUE, what value aesthetic value should missing be displayed as? Does not apply to position scales where NA is always placed at the far right.

aesthetics

The names of the aesthetics that this scale works with

scale_name

The name of the scale

name

The name of the scale. Used as the axis or legend title. If waiver(), the default, the name of the scale is taken from the first mapping used for that aesthetic. If NULL, the legend title will be omitted.

labels

One of:

  • NULL for no labels

  • waiver() for the default labels computed by the transformation object

  • A character vector giving labels (must be same length as breaks)

  • A function that takes the breaks as input and returns labels as output

expand

Vector of range expansion constants used to add some padding around the data, to ensure that they are placed some distance away from the axes. Use the convenience function expand_scale() to generate the values for the expand argument. The defaults are to expand the scale by 5% on each side for continuous variables, and by 0.6 units on each side for discrete variables.

guide

A function used to create a guide or its name. See guides() for more info.

position

The position of the axis. "left" or "right" for vertical scales, "top" or "bottom" for horizontal scales

super

The super class to use for the constructed scale
start

grey value at low end of palette
end

grey value at high end of palette
na.value

Colour to use for missing values
aesthetics

Character string or vector of character strings listing the name(s) of the aesthetic(s) that this scale works with. This can be useful, for example, to apply colour settings to the colour and fill aesthetics at the same time, via aesthetics = c("colour", "fill").

See also

Other colour scales: scale_alpha, scale_colour_brewer, scale_colour_gradient, scale_colour_hue, scale_colour_viridis_d

Examples

p <- ggplot(mtcars, aes(mpg, wt)) + geom_point(aes(colour = factor(cyl)))
p + scale_colour_grey()
p + scale_colour_grey(end = 0)

# You may want to turn off the pale grey background with this scale
p + scale_colour_grey() + theme_bw()

# Colour of missing values is controlled with na.value:
miss <- factor(sample(c(NA, 1:5), nrow(mtcars), replace = TRUE))
ggplot(mtcars, aes(mpg, wt)) +
  geom_point(aes(colour = miss)) +
  scale_colour_grey()
ggplot(mtcars, aes(mpg, wt)) +
  geom_point(aes(colour = miss)) +
  scale_colour_grey(na.value = "green")