How to annotate() ggplot with latex

Question

I'd like to add latex text to a ggplot2 plot using annotate(). Using expression(), as described here for adding latex to axis labels, does not seem to work. To wit:

# Use expression() to create subscripted text p <- ggplot(mpg, aes(x=cty, y=hwy)) + geom_point() +   scale_x_continuous(expression(text[subscript]))   # But expression() in annotate adds nothing to the plot p + annotate("text", x=10, y=40, label=expression(text[subscript]))   # Passing regular text to annotate works fine p + annotate("text", x=10, y=40, label="foo")  

Why are expressions treated differently by annotate than by other ggplot functions? And how can I annotate with latex?

Answer 1

There is an R package called latex2exp which may be helpful. It has function TeX which accepts some LaTeX expressions enclosed with dollar sign $ as in this example:

library(latex2exp) library(ggplot2)  qplot(1, "A")+      ylab(TeX("Formula: $\\frac{2hc^2}{\\lambda^\\beta}$"))+      xlab(TeX("$\\alpha$")) 

More examples can be found in this vignette.