在R - 表达式（）中显示*（星）上标

Question

is there any way to display superscript of *(star), with the expression() function? I am trying to display this in a graph produced in ggplot2. I have tried

expression(a^{*})

but does not work. Thank you.

Answer 1

plot(rnorm(30), xlab = expression(paste("a"^"*")))