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?

Helps if you include a bit of code to illustrate your problem. — Spacedman, Dec 31 '12 at 20:30

score 50 · Accepted Answer · answered Dec 31 '12 at 09:57

50

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

answered Dec 31 '12 at 09:57

agstudy

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another convenient possibility is something like `adjustcolor("red",alpha.f=0.5)` – Ben Bolker Dec 31 '12 at 16:20
@BenBolker, this should be an answer! – Nemesi Feb 03 '20 at 17:28

Ben Bolker · Answer 2 · 2022-09-08T18:23:52.267

13

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

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

edited Sep 08 '22 at 18:23

answered Feb 03 '20 at 20:03

Ben Bolker

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Transparency with polygon command

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