writing $^*$ in R's matplot

Question

I'm trying to represent $r^*$ in R matplot:

expression(r^*(bold(X)))

but the interpreter seems to get caught at the '^*' part. Any solutions?

Answer 1

Try this:

plot.new()
text(0.5,0.5,expression(r^"*"*(bold(X))))

A raw * is used to separate (juxtapose) the plotted expressions, see ?plotmath. Here, you wish to print an asterisk as plain text.