Use superscripts in R axis labels

Question

Using base graphics in R, how can I add superscripts to axis labels, as one might want to when plotting latitude and longitude axes on a map.

Consider this example:

plot(-100:-50, 50:100, type="n", xlab="", ylab="", axes=FALSE)
axis(1, seq(-100, -50, 10), labels=paste(abs(seq(-100, -50, 10)), "o", "W", sep=""))
axis(2, seq(50, 100, 10), labels=paste(seq(50,100,10), "o", "N", sep=""))
box()

Produces a nice frame around a map. It would be even nicer to make the degree symbol superscript.

This can usually be done in other plotting functions such as mtext() and text() using expression(paste(...)) or substitute() but how to do it in this case?

Does this `plot(0,xlab=expression(paste('(SOC[',kgm^-2,'])'^0.25,sep='')))` answer your question? — Eric Fail, May 17 '12 at 00:54

score 49 · Accepted Answer · answered May 17 '12 at 00:59

49

It works the same way for axes: parse(text='70^o*N') will raise the o as a superscript (the *N is to make sure the N doesn't get raised too).

labelsX=parse(text=paste(abs(seq(-100, -50, 10)), "^o ", "*W", sep=""))
labelsY=parse(text=paste(seq(50,100,10), "^o ", "*N", sep=""))
plot(-100:-50, 50:100, type="n", xlab="", ylab="", axes=FALSE)
axis(1, seq(-100, -50, 10), labels=labelsX)
axis(2, seq(50, 100, 10), labels=labelsY)
box()

answered May 17 '12 at 00:59

mathematical.coffee

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Text mark-up in plots is a bit of an obscure area of R practice. It always seems to mess me up. Thanks for this clarity. It would be great if someone developed an in depth tutorial for this. – digitalmaps May 17 '12 at 01:22
What character is used to indicate a subscript? – hendra Sep 04 '13 at 00:41
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@npo: square brackets (see `?plotmath`) – Ben Bolker Nov 04 '13 at 20:24
This breaks on text; Example: parse(text="Frequency ((364 days)^-1)") Needed superscript for axis title. No solution found myself. – Gullydwarf Sep 03 '15 at 14:32
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`plot(0,xlab=expression('Frequency (364 days)' ^ -1))` – mathematical.coffee Sep 03 '15 at 23:55

score 42 · Answer 2 · answered May 17 '12 at 01:04

42

This is a quick example

plot(rnorm(30), xlab = expression(paste("4"^"th")))

answered May 17 '12 at 01:04

Alex

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How would you write something not in superscript at the end, as in "4th moment" without superscripting the "moment"? – Pertinax Jul 17 '17 at 14:17
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@TheThunderChimp Sorry for the very late reply. Maybe you've already figured out how to do this, but you can do this: `plot(rnorm(30), xlab = expression(paste("4"^"th", " moment")))` – Alex Aug 31 '17 at 16:43
I have the same puzzle....where do I put the "" in this instance to have the -1 (only) in superscript? i.e..... + ylab = expression (paste("Ba:Ca concentration (μmol:mol^-1)") – Angela Russell Oct 27 '21 at 05:15

score 4 · Answer 3 · edited Dec 20 '17 at 22:33

4

@The Thunder Chimp You can split text in such a way that some sections are affected by super(or sub) script and others aren't through the use of *. For your example, with splitting the word "moment" from "4th" -

plot(rnorm(30), xlab = expression('4'^th*'moment'))

edited Dec 20 '17 at 22:33

Stedy

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answered Aug 25 '17 at 12:45

R Ramsay

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score 3 · Answer 4 · answered Apr 16 '14 at 05:33

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The other option in this particular case would be to type the degree symbol: ˚

R seems to handle it fine. Type Option-k on a Mac to get it. Not sure about other platforms.

answered Apr 16 '14 at 05:33

Stewart Macdonald

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This does not work for other symbols like Unicode superscript 7 (http://www.fileformat.info/info/unicode/char/2077/index.htm) – Pertinax Jul 17 '17 at 14:12

Use superscripts in R axis labels

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