Multicolor titles with ggplot2 for R

Question

I was trying to implement multicolor texts as shown here:

multicolor text on chart

which referenced this:

multicolor text in R

This is what I

Answer 1

Here's a more general approach that takes advantage of a few additional grid functions. It's not particularly well-polished, but it may give you some useful ideas:

library(grid)
library(ggplot2)

p <- ggplot(data=mtcars, aes(mpg,hp,color=factor(cyl),size=2)) + 
       geom_point() + theme_bw() +
       opts(title = " \n ") + opts(legend.position="none")

## Get factor levels 
levs <- levels(factor(mtcars$cyl))
n <- length(levs)

## Get factors' plotting colors
g <- ggplot_build(p)
d <- unique(g$data[[1]][c("colour", "group")])
cols <- d$colour[order(d$group)]

## Use widest label's width to determine spacing
labs <- paste(levs, "cylinder")
xlocs <- unit(0.5, "npc") + 
         1.1 * (seq_len(n) - mean(seq_len(n))) * max(unit(1, "strwidth", labs))

## Plot labels in top 10% of device
pushViewport(viewport(y=0.95, height=0.1))
    grid.text(paste(levs, "cylinder"), 
              x = xlocs, y=unit(0.5, "lines"), 
              gp = gpar(col=cols, fontface="bold"))
    grid.text("- Horsepower versus Miles per Gallon", 
              y = unit(-0.5, "lines"))
upViewport()

## Plot main figure in bottom 90% of device
pushViewport(viewport(y=0.45, height=0.9))
    print(p, newpage=FALSE)
upViewport()