spatstat (version 1.20-2)

colourmap: Colour Lookup Tables

Description

Create a colour map (colour lookup table).

Usage

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

Arguments

col

Character vector specifying colours

...

Ignored.

inputs

Values to which the colours are associated. A factor or vector of the same length as col. Incompatible with breaks.

breaks

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

Value

• A function, which is also an object of class "colourmap".

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 spatstat package. It can also be used to compute the colour assigned to any data value.

The argument 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 inputs and 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 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 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 spatstat package accept an object of this class as a specification of the colour map.

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.

See Also

The plot method plot.colourmap. See colours for information about the colours that Rrecognises, and how to manipulate them.

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), 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)