scales (version 0.4.1)

col_numeric: Color mapping


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


col_numeric(palette, domain, na.color = "#808080")
col_bin(palette, domain, bins = 7, pretty = TRUE, na.color = "#808080")
col_quantile(palette, domain, n = 4, probs = seq(0, 1, length.out = n + 1), na.color = "#808080")
col_factor(palette, domain, levels = NULL, ordered = FALSE, na.color = "#808080")


The colors or color function that values will be mapped to
The possible values that can be mapped.

For col_numeric and col_bin, this can be a simple numeric range (e.g. c(0, 100)); col_quantile needs representative numeric data; and col_factor 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.

The color to return for NA values. Note that na.color=NA is valid.
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.
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".
Number of equal-size quantiles desired. For more precise control, use the probs argument instead.
See quantile. If provided, the n argument is ignored.
An alternate way of specifying levels; if specified, domain is ignored
If TRUE and domain needs to be coerced to a factor, treat it as already in the correct order


A function that takes a single parameter x; when called with a vector of numbers (except for col_factor, which expects factors/characters), #RRGGBB color strings are returned.


col_numeric is a simple linear mapping from continuous numeric data to an interpolated palette.

col_bin also maps continuous numeric data, but performs binning based on value (see the cut function).

col_quantile similarly bins numeric data, but via the quantile function.

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


pal <- col_bin("Greens", domain = 0:100)
show_col(pal(sort(runif(10, 60, 100))))

# Exponential distribution, mapped continuously
show_col(col_numeric("Blues", domain = NULL)(sort(rexp(16))))
# Exponential distribution, mapped by interval
show_col(col_bin("Blues", domain = NULL, bins = 4)(sort(rexp(16))))
# Exponential distribution, mapped by quantile
show_col(col_quantile("Blues", domain = NULL)(sort(rexp(16))))

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