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?

Answer 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)