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mages/add.alpha.R

Last active December 20, 2018 14:31
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How to change the alpha value of colours in R
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add.alpha.R
## Add an alpha value to a colour
add.alpha <- function(col, alpha=1){
if(missing(col))
stop("Please provide a vector of colours.")
apply(sapply(col, col2rgb)/255, 2,
function(x)
rgb(x[1], x[2], x[3], alpha=alpha))
}
@danlewer
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rgb and col2rgb are both vectorized. Perhaps:

add.alpha <- function(cols, alpha) rgb(t(col2rgb(cols)/255), alpha = alpha)

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