Is there a way to define multiple aesthetics in scale_discrete_manual?

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I was looking through scale_discrete_manual ggplot element, I could find only example for combined aesthetics with the same values, like fill and color, like here:

library(ggplot2)

data <- data.frame(x = 1:10, y = 1:10, group = factor(rep(1:2, length.out = 10)))

ggplot(data, aes(x = x, y = y, color = group, fill = group)) + 
 geom_line() + 
 scale_discrete_manual(c("color", "fill"), values = c("yellow", "darkred"))

But I couldn't find any example or description whether it is possible to do the same for aesthetics with different type values, like color and linetype.

library(ggplot2)

data <- data.frame(x = 1:10, y = 1:10, group = factor(rep(1:2, length.out = 10)))

# It gives an error
ggplot(data, aes(x = x, y = y, color = group, linetype = group)) + 
 geom_line() + 
 scale_discrete_manual(c("color", "linetype"), values = c("yellow", "darkred", "solid", "dashed"))

I know that it is possible to do what I need in 2 separate calls to scale_discrete_manual or with custom function which can incapsulate those calls, but I am interested whether it is possible to do the same only in 1 call in native to ggplot way?

UPDATE

At the moment, I have settled with custom function, which does exactly what I need:

scale_discrete_manual_ext <- function(aesthetics, values, name)
{
  lapply(aesthetics, function(aesthetic) {
    ggplot2::scale_discrete_manual(aesthetic, values = values[[aesthetic]], name = name)
  })
}

# Usage
ggplot(data, aes(x = x, y = y, color = group, linetype = group)) + 
 geom_line() + 
 scale_discrete_manual_ext(c("color", "linetype"), values = list(color = c("yellow", "darkred"),linetype = c("solid", "dashed")), name = "Legend name")

However the question is still opened.

ggplot2 r
1 Answers

I guess the problem is, that ggplot tries to map the values provided to scale_discrete_manual to all aesthetics and "solid" is no color.

Only solution I'd see is, to use separate scales like here:

ggplot(data, aes(x = x, y = y, color = group, fill = group, linetype = group)) + 
 geom_line(size = 3) + 
 scale_discrete_manual(c("color", "fill"), values = c("yellow", "darkred")) +
 scale_linetype_manual(values = c("dashed", "dotted"))
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