ggplot2: Bring one line to the front, but save the colors

Question

Consider the following code:

library(ggplot2)
foo <- data.frame(x=1:10,A=1:10,B=10:1)
ggplot(melt(foo,id.vars=\"x\"),aes(x,value,color=variable))+geom_lin         


        

Answer 1

The solution with replotting is fine unless you have reasons to avoid it. I can think of at least two: using alpha (transparency) or performance issues (you need to do it in one run, big data).

Here's what I propose:

require(scales)
# give the desired order here, I just use reverse
# separate function since we apply it over both levels & colors
shuffle <- function(x) rev(x)
foo <- data.frame(x=1:10, A=1:10, B=10:1, C=2.5, D=7.5)
melt_foo <- melt(foo, id.vars="x") 
# original plot
ggplot(melt_foo, aes(x, value, color=variable)) + 
  geom_line(size=5)

orig_order <- levels(melt_foo$variable)
new_order <- shuffle(orig_order)
# grabbing default colours
orig_colors <- hue_pal()(length(new_order))
new_colors <- shuffle(orig_colors)
melt_foo$variable <- factor(melt_foo$variable, levels=new_order)
# levels _and_ colours reversed, legend appearance stays the same
ggplot(melt_foo, aes(x, value, color=variable)) + 
  geom_line(size=5) + 
  scale_colour_manual(values=new_colors, labels=orig_order, breaks=orig_order)