Add and set alpha channel for RGB color

Add and set alpha channel

col.alpha(col, alpha = 1)

Arguments

col	a vector of RGB color(s)
alpha	numeric value between 0 and 1. Zero results fully transparent and 1 means full opacity

Details

This function adds and set an alpha channel to a RGB color

References

Ekstrom, CT (2011) The R Primer.

Examples

newcol <- col.alpha("blue", .5)