Combine an expression and a new line in ggplot2 legend

Question

I'm probably asking too much, anyway I would like to create a legend title on two lines, where the first line contains an expression (the greek symbol \\Phi, with subscript 10 ), and the second line is [.] . It should look like this:

I tried

p <- ggplot(mtcars,aes(x=wt,y=mpg,color=qsec))+
     geom_point()+
     labs(color=expression(atop(Phi["10"]),group("[",.,"]")))

But this doesn't print the lower line:

Can you help?

Answer 1

You simply have a bracket in the wrong place. It should be atop(something, somethingelse)

p <- ggplot(mtcars,aes(x=wt,y=mpg,color=qsec))+
     geom_point()+
     labs(color=expression(atop(Phi["10"],group("[",.,"]"))))