col.alpha: Color utility functions
In joepowers16/rethinking: Statistical Rethinking book package

Description Usage Arguments Details Author(s) See Also

Functions for calculating transparent and desaturated colors.

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col.alpha( acol , alpha = 0.2 )
col.desat( acol , amt = 0.5 )
col.dist( x , mu = 0 , sd = 1 , col="slateblue" )

`acol`	A color name or RGB color
`alpha`	alpha transparency, where 1 means fully opaque and 0 fully transparent
`amt`	amount of desaturation of color to apply, where 1 means totally desaturated (grayscale)
`x`	A vector of values to use for calculating distances. See details below.
`mu`	Value (or vector of values) to use for calculating distances
`sd`	Standard deviation of distance function used to calculate transparency
`col`	A color to apply transparency to, based on distance

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.

Richard McElreath

col2rgb, rgb2hsv, rgb

joepowers16/rethinking documentation built on June 2, 2019, 6:52 p.m.