pHcolourmap: Colour Map for pH Values

In spatstat.geom: Geometrical Functionality of the 'spatstat' Family

Colour Map for pH Values

Description

Create a colour map for values of pH.

Usage

 pHcolourmap(range = c(0, 14), ..., n=256, step = FALSE)
 pHcolour(pH)

Arguments

n	Number of different colour values to be used, when step=FALSE.
range	Range of pH values that will be accepted as inputs to the colour map. A numeric vector of length 2 giving the minimum and maximum values of pH.
step	Logical value. If step=FALSE (the default) the colours change continuously with increasing values of the input. If step=TRUE, the colour is constant on each unit interval of pH values.
...	Ignored.
pH	Numerical value or numeric vector of values of pH.

Details

In chemistry the hydrogen potential pH measures how acidic or basic a solution is.

The function pHcolour calculates the colour associated with a given value of pH, according to a standard mapping in which neutral pH=7 is green, acidic values pH < 7 are yellow or red, and basic values pH > 7 are blue. The function pHcolour takes a numerical value or vector of values of pH and returns a character vector containing the corresponding colours.

The function pHcolourmap produces a colour map for numerical values of pH, using the same consistent mapping of pH values to colours. The argument range specifies the range of pH values that will be mapped by the resulting colour map. It should be a numeric vector of length 2 giving the minimum and maximum values of pH that the colour map will handle. (Colour maps created with different values of range use essentially the same mapping of colours, but when plotted as colour ribbons, display only the specified range.)

If step=FALSE (the default) the colours change continuously with increasing values of the input. There will be n different colour values in the colour map. Usually n should be a large number.

If step=TRUE, the colour is constant on each unit interval of pH values. That is, any value of pH in the interval [k, k+1], where k is an integer, will be mapped to the same colour.

Value

The return value of pHcolour is a character string or a vector of character strings representing colours.

The return value of pHcolourmap is a colour map (object of class "colourmap").

Author(s)

\adrian

.

See Also

colourmap

Examples

  pHcolour(7)

  plot(pHcolourmap())
  plot(pHcolourmap(step=TRUE))
  plot(pHcolourmap(c(3, 8)))

spatstat.geom documentation built on Sept. 18, 2024, 9:08 a.m.