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Color mapping

Source: R/colors.R
colorNumeric.Rd

Conveniently maps data values (numeric or factor/character) to colors according to a given palette, which can be provided in a variety of formats.

Usage

colorNumeric(
  palette,
  domain,
  na.color = "#808080",
  alpha = FALSE,
  reverse = FALSE
)

colorBin(
  palette,
  domain,
  bins = 7,
  pretty = TRUE,
  na.color = "#808080",
  alpha = FALSE,
  reverse = FALSE,
  right = FALSE
)

colorQuantile(
  palette,
  domain,
  n = 4,
  probs = seq(0, 1, length.out = n + 1),
  na.color = "#808080",
  alpha = FALSE,
  reverse = FALSE,
  right = FALSE
)

colorFactor(
  palette,
  domain,
  levels = NULL,
  ordered = FALSE,
  na.color = "#808080",
  alpha = FALSE,
  reverse = FALSE
)

Arguments

palette

The colors or color function that values will be mapped to

domain

The possible values that can be mapped.

For colorNumeric() and colorBin(), this can be a simple numeric range (e.g., c(0, 100)); colorQuantile() needs representative numeric data; and colorFactor() needs categorical data.

If NULL, then whenever the resulting color function is called, the x value will represent the domain. This implies that if the function is invoked multiple times, the encoding between values and colors may not be consistent; if consistency is needed, you must provide a non-NULL domain.

na.color

The color to return for NA values. Note that na.color = NA is valid.

alpha

Whether alpha channels should be respected or ignored. If TRUE then colors without explicit alpha information will be treated as fully opaque.

reverse

Whether the colors (or color function) in palette should be used in reverse order. For example, if the default order of a palette goes from blue to green, then reverse = TRUE will result in the colors going from green to blue.

bins

Either a numeric vector of two or more unique cut points or a single number (greater than or equal to 2) giving the number of intervals into which the domain values are to be cut.

pretty

Whether to use the function pretty() to generate the bins when the argument bins is a single number. When pretty = TRUE, the actual number of bins may not be the number of bins you specified. When pretty = FALSE, seq() is used to generate the bins and the breaks may not be "pretty".

right

parameter supplied to cut. See Details

n

Number of equal-size quantiles desired. For more precise control, use probs instead.

probs

See stats::quantile(). If provided, n is ignored.

levels

An alternate way of specifying levels; if specified, domain is ignored

ordered

If TRUE and domain needs to be coerced to a factor, treat it as already in the correct order

Value

A function that takes a single parameter x; when called with a vector of numbers (except for colorFactor(), which expects factors/characters), #RRGGBB color strings are returned (unless alpha = TRUE in which case #RRGGBBAA may also be possible).

Details

colorNumeric() is a simple linear mapping from continuous numeric data to an interpolated palette.

colorBin() also maps continuous numeric data, but performs binning based on value (see the base::cut() function). colorBin() defaults for the base::cut() function are include.lowest = TRUE and right = FALSE.

colorQuantile() similarly bins numeric data, but via stats::quantile().

colorFactor() maps factors to colors. If the palette is discrete and has a different number of colors than the number of factors, interpolation is used.

The palette argument can be any of the following:

  1. A character vector of RGB or named colors. Examples: palette(), c("#000000", "#0000FF", "#FFFFFF"), topo.colors(10)

  2. The name of an RColorBrewer palette, e.g., "BuPu" or "Greens".

  3. The full name of a viridis palette: "magma", "inferno", "plasma", "viridis", "cividis", "rocket", "mako", or "turbo"

  4. A function that receives a single value between 0 and 1 and returns a color. Examples: colorRamp(c("#000000", "#FFFFFF"), interpolate = "spline").

Examples

pal <- colorBin("Greens", domain = 0:100)
pal(runif(10, 60, 100))
#>  [1] "#31A354" "#006D2C" "#006D2C" "#31A354" "#31A354" "#006D2C"
#>  [7] "#31A354" "#31A354" "#31A354" "#31A354"

if (interactive()) {
  # Exponential distribution, mapped continuously
  previewColors(colorNumeric("Blues", domain = NULL), sort(rexp(16)))
  # Exponential distribution, mapped by interval
  previewColors(colorBin("Blues", domain = NULL, bins = 4), sort(rexp(16)))
  # Exponential distribution, mapped by quantile
  previewColors(colorQuantile("Blues", domain = NULL), sort(rexp(16)))

  # Categorical data; by default, the values being colored span the gamut...
  previewColors(colorFactor("RdYlBu", domain = NULL), LETTERS[1:5])
  # ...unless the data is a factor, without droplevels...
  previewColors(colorFactor("RdYlBu", domain = NULL), factor(LETTERS[1:5], levels = LETTERS))
  # ...or the domain is stated explicitly.
  previewColors(colorFactor("RdYlBu", levels = LETTERS), LETTERS[1:5])
}