R plot title with greek letter, newline and variable value

Question

I am trying to plot a title, a greek character and as well the mean of a variable. I want my plot title to look something like this (but centered)

Title

μ=1.2

I made a few attepmts:

d <- rnorm(100)
hist(d, main=expression(paste("Title\n", mu, "=", mean(d))))
hist(d, main=expression(paste("Title\n", mu, "=", mymean), list(mymean=mean(d))))
hist(d, main=paste(expression(paste("Title\n", mu, "="), mean(d))))
hist(d, main=expression(atop("Title", substitute(mu, "=", mymean, list(mymean=mean(d))))))
hist(d, main=expression("Title\n", substitute(mu, "=", mymean, list(mymean=mean(d)))))

but I don't know how to use expression or substitute correctly in the title. I know that mtext would be a possibility, but it should work using the main= argument...?

Answer 1

You can do this with atop :

hist(d, main=bquote(atop(Title,mu==.(mean(d)))))

Answer 2

Use the plain() function to specify normal text and * , ~ and ~~ as a spacers:

mtext(main=bquote(plain("Observation at pH ") ~ .(pH) ~~ plain(" [") *  mu * plain("M]")))

This is explained somewhat cryptically in ?plain (which translates into help regarding plain, when typed in the R command line prompt). You will then get the help page Mathematical Annotation in R , then search for plain in that page.