How to write x-axis title with text and superscript ggplot2

Question

I would like to write the below title at an x-axis using the following code:

Title: Grain yield (ton. ha-1)

labs(x=expression(bold(paste("Grain yield","  ","(ton.", ha^-1,")", sep=""))))

-1 should be superscripted and the entire title should be in bold. I am getting everything right excepted that the superscripted part is not in bold.

I appreciate any help.

Thanks!

Answer 1

It's rather unusual to get incorrect advice from @BenBolker, but here is the solution to what he was offering as an example of a problem without solution:

barplot(height=c(1,1), ylab=expression(bold(paste("org.", cm^bold("-2")))))

The trick here is not to use numeric but rather text arguments. In your case you are under the common misconception that paste in plotmath has a 'sep' argument. It doesn't. (Furthermore it is generally not needed if you learn to use "~" and "*" properly.) This is a paste()-less solution:

plot(1,1, xlab=expression(bold(Grain~yield~~"(ton."*ha^"-1"*")")))

(I tested it with a base graphic because you didn't offer a complete example. There is no lab function in base R.)

Answer 2

@Dwin thanks for you answer I just needed to make a small modification on the code you showed:

xlab=expression(bold(Grain~yield~~"(ton."*ha^"-1"*")")))

this code did not work on my entire code background back I changed it to

xlab(expression(bold(Grain~yield~~"(ton."*ha^"-1"*")")))

changed the signal = for ( and it worked perfectly.

Thank you very much!!!