# colourmap

##### Colour Lookup Tables

Create a colour map (colour lookup table).

##### Usage

`colourmap(col, ..., range=NULL, breaks=NULL, inputs=NULL)`

##### Arguments

- col
- Vector of values specifying colours
- ...
- Ignored.
- range
- Interval to be mapped.
A numeric vector of length 2, specifying the endpoints of the
range of values to be mapped.
Incompatible with
`breaks`

or`inputs`

. - inputs
- Values to which the colours are associated.
A factor or vector of the same length as
`col`

. Incompatible with`breaks`

or`range`

. - breaks
- Breakpoints for the colour map.
A numeric vector of length equal to
`length(col)+1`

. Incompatible with`range`

or`inputs`

.

##### Details

A colour map is a mechanism for associating colours with data. It can be regarded as a function, mapping data to colours.

The command `colourmap`

creates an object representing
a colour map, which can then be used to control the plot commands
in the

The argument `col`

specifies the colours to which
data values will be mapped. It should be a vector
whose entries can be interpreted as colours by the standard
Rgraphics system. The entries can be string names of colours
like `"red"`

, or integers that refer to
colours in the standard palette, or strings containing
six-letter hexadecimal codes like `"#F0A0FF"`

.

Exactly one of the arguments `range`

, `inputs`

or `breaks`

must be specified by name.

If `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 `inputs[i]`

with the colour `col[i]`

.

If `range`

is given, then it determines the interval of the real
number line that will be mapped. It should be a numeric vector of
length 2.

If `breaks`

is given, then it determines the precise 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
between `breaks[i]`

and `breaks[i+1]`

will be mapped to the
colour `col[i]`

.

The result is an object of class `"colourmap"`

.
There are `print`

and `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.
That is, `f(x)`

returns the character value of the colour assigned
to `x`

. This also works for vectors of data values.

##### Value

- A function, which is also an object of class
`"colourmap"`

.

##### See Also

The plot method `plot.colourmap`

.
See the Rhelp file on
`colours`

for information about the colours
that Rrecognises, and how to manipulate them.
See `colourtools`

for more tools to manipulate colours.
See `lut`

for lookup tables.

##### Examples

```
# 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), range=c(-1,1))
co(0.2)
# colour map for discrete set of values
ct <- colourmap(c("red", "green"), inputs=c(FALSE, TRUE))
ct(TRUE)
```

*Documentation reproduced from package spatstat, version 1.23-2, License: GPL (>= 2)*