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.
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".
n
Number of equal-size quantiles desired. For more precise control,
use the probs argument instead.
probs
See quantile. If provided, the n
argument 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
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 cut function).
colorQuantile similarly bins numeric data, but via the
quantile function.
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:
A character vector of RGB or named colors. Examples: palette(), c("#000000", "#0000FF", "#FFFFFF"), topo.colors(10)
The name of an RColorBrewer palette, e.g. "BuPu" or "Greens".
A function that receives a single value between 0 and 1 and returns a color. Examples: colorRamp(c("#000000", "#FFFFFF"), interpolate="spline").
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).
Examples
pal = colorBin("Greens", domain = 0:100)
pal(runif(10, 60, 100))
# 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])