Transparency with polygon command

Question

I used the polygon command in R which created an area in the plot. However, the values in this area are not shown whereas the main aim is to monitor these values. Does anyone know how to handle this?

Solution 1

You can use The function rgb() to specify a color with an alpha transparency.

for example :

xx <- c(1:50)
 yy <- rnorm(50)
 n <- 50
 hline <- 0
plot (yy ~ xx, type="n", axes=FALSE, ann=FALSE)
text(x=xx,y=min(yy)+max(yy),labels='a')
polygon(c(xx[1], xx, xx[n]), c(min(yy), yy, min(yy)),    
        col=rgb(1, 0, 0,0.5), border=NA)

Solution 2

Another convenient possibility for making a lighter/more-transparent version of an existing is to use adjustcolor(), something like

adjustcolor("red",alpha.f=0.5) 

Comments

[Spacedman]

Helps if you include a bit of code to illustrate your problem.

[Ben Bolker]

another convenient possibility is something like adjustcolor("red",alpha.f=0.5)

[Nemesi]

@BenBolker, this should be an answer!