Concatenate strings and expressions in a plot's title

Question

How can I combine text and math expressions in a plot's title. If I use paste the expression is converted to character. For example I want something like this as a title

$ARL_1$ curve for $S^2$

Thank you

Faulk

Answer 1

You want to read ?plotmath to see how to do this sort of thing. Here is an example:

plot(1:10, main = expression(ARL[1] ~ "curve for" ~ S^2))

The [.] is subscript, whilst ^ gives superscript. The ~ spaces out the parts of the expression as if there were literal spaces.

Edit: normally I would have done:

plot(1:10, main = expression(ARL[1] ~ curve ~ for ~ S^2))

but that throws an error because for is being interpreted as the start of a for() loop call.

Jubilate

Second will work if you use expression(ARL[1] ~ curve ~ "for" ~ S^2). – Glottology

@Marek: Oh, yes, agreed. But if you are going to do "for" you might as well do "curve for", unless ~ and " " are different amounts of space...? – Jubilate

Of course. It matters in more complicated cases when one needs to mixed more strings. I add it as completeness ;) On other hand you could also use back-ticks `. – Glottology

Answer 2

You can also use bquote(paste(...)), which is a little more flexible than expression: you can include variable values (say, the value of x) in the labels with .(x). For example:

x<- 232323
plot(1:10, main = bquote(paste(ARL[1], " curve for ", S^2, "; x=",.(x))))

Eikon

Yes although I generally find that using the plotmath paste function confuses more than it helps. Try > x<- 232323 > plot(1:10, main = bquote(ARL[1]~"curve for"~S^2~";"~x==.(x))) – Joviality

+1 Dwin - introducing paste is a pain in the but if you get your , or "" in the wrong places... – Jubilate

@GavinSimpson Yeah, your answer is nicer. But I thought it would be good to point out a more flexible solution in case somebody comes here looking for a more general solution. – Eikon

+1 from me. That comment wasn't a criticism of the substantive point of your answer (bquote()), just a point about introducing paste in there if you can avoid it. bquote() is underused and very powerful! – Jubilate

.. another 1+ from me. I thought bquote was an excellent suggestion and only added a very minor demurral to avoid paste when possible, because it often gets confused with that "other paste". People don't realize it's a different function with different sematics and with no sep argument. – Joviality

Answer 3

You can also use latex2exp::TeX to convert TeX to expressions on the fly:

plot(cars, main = TeX("$ARL_1$ curve for $S^2$"))

Hardened