Colour Lookup Tables
Create a colour map (colour lookup table).
colourmap(col, ..., breaks=NULL, inputs=NULL)
- Character vector specifying colours
- Values to which the colours are associated.
A factor or vector of the same length as
col. Incompatible with
- Breakpoints for the colour map.
A numeric vector of length equal to
A colour map is a mechanism for associating colours with data. It can be regarded as a function, mapping data to colours.
colourmap creates an object representing
a colour map, which can then be used to control the plot commands
col specifies the colours to which
data values will be mapped. It should be a character vector
whose entries can be interpreted as colours.
Exactly one of the arguments
must be specified by name.
inputs is given, then it should be a vector or factor,
of the same length as
col. The entries of
inputs can be
any atomic type (e.g. numeric, logical, character, complex) or factor
values. The resulting colour map associates the value
with the colour
breaks is given, then it determines intervals
of the real number line
which are mapped to each colour. It should be a numeric vector,
of length at least 2, with entries that are in increasing order.
Infinite values are allowed. Any number in the range
breaks[i+1] will be mapped to the
The result is an object of class
plot methods for this class.
Some plot commands in the
The result is also a function
f which can be used to compute
the colour assigned to any data value.
f(x) returns the character value of the colour assigned
x. This also works for vectors of data values.
- A function, which is also an object of class
lut for lookup tables.
# colour map for real numbers, using breakpoints cr <- colourmap(c("red", "blue", "green"), breaks=c(0,5,10,15)) cr cr(3.2) cr(c(3,5,7)) # a large colour map co <- colourmap(rainbow(100), breaks=seq(-1,1,length=101)) co(0.2) # colour map for discrete set of values ct <- colourmap(c("red", "green"), inputs=c(FALSE, TRUE)) ct(TRUE)