Transparency with polygon command

Kazo picture Kazo · Dec 31, 2012 · Viewed 29.8k times · Source

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?

Answer

agstudy picture agstudy · Dec 31, 2012

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)

enter image description here