Functions for calculating transparent and desaturated colors.
col.alpha( acol , alpha = 0.2 )
col.desat( acol , amt = 0.5 )
col.dist( x , mu = 0 , sd = 1 , col="slateblue" )
grau( alpha = 0.5 )A color name or RGB color
alpha transparency, where 1 means fully opaque and 0 fully transparent
amount of desaturation of color to apply, where 1 means totally desaturated (grayscale)
A vector of values to use for calculating distances. See details below.
Value (or vector of values) to use for calculating distances
Standard deviation of distance function used to calculate transparency
A color to apply transparency to, based on distance
Transparency of black (used by grau function)
These functions allow for calculating transparency and desaturation for colors. col.alpha makes a base color transparent, while col.desat makes a color have less saturation.
col.dist is used to make a list of transparent colors of differing alpha level. The levels are chosen based upon Gaussian distance from a chosen value, mu, with a chosen width of the function that determines how quickly colors become fully transparent, sd. For example, if x contains a column of data, then col.dist will return a vector of same length with transparency increasing as each value in x is distant from mu. This is useful for plotting data that emphasize points near some value or values.
grau simply returns a transparent version of black, producing effective gray values.