Add an Alpha Channel To a Color
Add transparency to a color defined by its name or number. The function first converts the color to RGB and then appends the alpha channel.
SetAlpha(col, alpha = 0.5)
col |
vector of two kind of R colors, i.e., either a color name (an element of |
alpha |
the alpha value to be added. This can be any value from 0 (fully transparent) to 1 (opaque). |
All arguments are recyled as necessary.
Vector with the same length as col, giving the rgb-values extended by the alpha channel as hex-number (#rrggbbaa).
Andri Signorell <andri@signorell.net>
SetAlpha("yellow", 0.2)
SetAlpha(2, 0.5) # red
Canvas(3)
DrawCircle(x=c(-1,0,1), y=c(1,-1,1), r.out=2, col=SetAlpha(2:4, 0.4))
x <- rnorm(15000)
par(mfrow=c(1,2))
plot(x, type="p", col="blue" )
plot(x, type="p", col=SetAlpha("blue", .2), main="Better insight with alpha channel" )Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.