R: Gradient colour scales

scale_colour_gradient {ggplot2}

R Documentation

Gradient colour scales

Description

scale_*_gradient creates a two colour gradient (low-high), scale_*_gradient2 creates a diverging colour gradient (low-mid-high), scale_*_gradientn creats a n-colour gradient.

Usage

scale_colour_gradient(..., low = "#132B43", high = "#56B1F7",
  space = "Lab", na.value = "grey50", guide = "colourbar",
  aesthetics = "colour")

scale_fill_gradient(..., low = "#132B43", high = "#56B1F7", space = "Lab",
  na.value = "grey50", guide = "colourbar", aesthetics = "fill")

scale_colour_gradient2(..., low = muted("red"), mid = "white",
  high = muted("blue"), midpoint = 0, space = "Lab",
  na.value = "grey50", guide = "colourbar", aesthetics = "colour")

scale_fill_gradient2(..., low = muted("red"), mid = "white",
  high = muted("blue"), midpoint = 0, space = "Lab",
  na.value = "grey50", guide = "colourbar", aesthetics = "fill")

scale_colour_gradientn(..., colours, values = NULL, space = "Lab",
  na.value = "grey50", guide = "colourbar", aesthetics = "colour", colors)

scale_fill_gradientn(..., colours, values = NULL, space = "Lab",
  na.value = "grey50", guide = "colourbar", aesthetics = "fill", colors)

Arguments

`...`	Arguments passed on to `continuous_scale` aesthetics The names of the aesthetics that this scale works with scale_name The name of the 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 name The name of the scale. Used as 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. breaks One of: `NULL` for no breaks `waiver()` for the default breaks computed by the transformation object A numeric vector of positions A function that takes the limits as input and returns breaks as output minor_breaks One of: `NULL` for no minor breaks `waiver()` for the default breaks (one minor break between each major break) A numeric vector of positions A function that given the limits returns a vector of minor breaks. 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 limits A numeric vector of length two providing limits of the scale. Use `NA` to refer to the existing minimum or maximum. rescaler Used by diverging and n colour gradients (i.e. `scale_colour_gradient2()`, `scale_colour_gradientn()`). A function used to scale the input values to the range [0, 1]. oob Function that handles limits outside of the scale limits (out of bounds). The default replaces out of bounds values with NA. trans Either the name of a transformation object, or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "exp", "identity", "log", "log10", "log1p", "log2", "logit", "probability", "probit", "reciprocal", "reverse" and "sqrt". A transformation object bundles together a transform, it's inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called `name_trans`, e.g. `scales::boxcox_trans()`. You can create your own transformation with `scales::trans_new()`. 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 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.
`low, high`	Colours for low and high ends of the gradient.
`space`	colour space in which to calculate gradient. Must be "Lab" - other values are deprecated.
`na.value`	Colour to use for missing values
`guide`	Type of legend. Use `"colourbar"` for continuous colour bar, or `"legend"` for discrete colour legend.
`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")`.
`mid`	colour for mid point
`midpoint`	The midpoint (in data value) of the diverging scale. Defaults to 0.
`colours, colors`	Vector of colours to use for n-colour gradient.
`values`	if colours should not be evenly positioned along the gradient this vector gives the position (between 0 and 1) for each colour in the `colours` vector. See `rescale()` for a convience function to map an arbitrary range to between 0 and 1.

Details

Default colours are generated with munsell and mnsl(c("2.5PB 2/4", "2.5PB 7/10")). Generally, for continuous colour scales you want to keep hue constant, but vary chroma and luminance. The munsell package makes this easy to do using the Munsell colour system.

Examples

df <- data.frame(
  x = runif(100),
  y = runif(100),
  z1 = rnorm(100),
  z2 = abs(rnorm(100))
)

# Default colour scale colours from light blue to dark blue
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z2))

# For diverging colour scales use gradient2
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z1)) +
  scale_colour_gradient2()

# Use your own colour scale with gradientn
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z1)) +
  scale_colour_gradientn(colours = terrain.colors(10))

# Equivalent fill scales do the same job for the fill aesthetic
ggplot(faithfuld, aes(waiting, eruptions)) +
  geom_raster(aes(fill = density)) +
  scale_fill_gradientn(colours = terrain.colors(10))

# Adjust colour choices with low and high
ggplot(df, aes(x, y)) +
  geom_point(aes(colour = z2)) +
  scale_colour_gradient(low = "white", high = "black")
# Avoid red-green colour contrasts because ~10% of men have difficulty
# seeing them