How to change the alpha value of colours in R
alpha channel
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R
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rgb
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Tutorials
4 comments
col2rgb and rgb, which has an argument for alpha, in combination with the wonderful apply and sapply functions. The example below illustrates how this function can be used with colours provided in different formats, thanks to the
col2rgb function. 
Session Info
sessionInfo()
R version 3.0.0 (2013-04-03)
Platform: x86_64-apple-darwin10.8.0 (64-bit)
locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] RCurl_1.95-4.1 bitops_1.0-5
4 comments :
Short and cool function!
i like to use ggplot2, it has built-in functions to do the same thing
library(ggplot2)
ggplot(dat, aes(x = x, y = y)) + #set up plot with data source and axis
geom_boxplot(outlier.colour=NA) + # add boxplots, suppress outliers
geom_point(position = "jitter", aes(col = factor(x)), alpha = .5) + #add jittered points, #colored by y, set alpha to .5
theme_bw() + # i prefer the bw theme
scale_color_brewer(type = "qual", palette = 6) # set color palette
There is adjustcolor function: adjustcolor(myColours, 0.4)
Brilliant! I didn't know this function existed.
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