Use Superscripts in R Axis Labels

Use superscripts in R axis labels

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()

How to subscript/superscript and italicize x-axis labels?

You can add subscripts/superscripts using expression(). Subscripts use [] and superscripts ^.

So: "KA(2,3)2": expression("KA"["2,3"]^2)

Since there is a comma in the (2,3) you need to put it in quotes (or you can add the comma separately: [2*","*3]

Superscript in axis labels in ggplot2 for ions

Try to put the superscript as a literal, between quotes.

g <- ggplot(iris, aes(Species, Sepal.Length)) + geom_boxplot()
g + xlab(bquote('Superscript as a literal' ~~ Ca^'2+'))

Superscript in brackets for my axis title

Try

xlab = expression(paste("spleen volume [cm"^3, "]"))

Special characters and superscripts on plot axis titles

The one thing that often users fail to grasp is that you invariably don't need to quote strings and paste them together when used in an expression for a plot label. It is usually simpler to use the layout tools directly (e.g. ~ and *). For example:

df <- data.frame(y = rnorm(100), x = rnorm(100))

plot(y ~ x, data = df,
     ylab = expression(Average ~ Conc ~ of ~ S- ~ on ~ plates ~ 
                       (mu ~ Moles ~ cm^{-2} ~ dry ~ wt)),
     xlab = expression(Concentration ~ Cl ~ (mu ~ moles ~ g^{-1} ~ dry ~ wt)))

Alternatively, you can include strings for longer sections of text; in this case it is arguably easier to do:

plot(y ~ x, data = df,
     ylab = expression("Average Conc of S- on plates" ~
                         (mu ~ moles ~ cm^{-2} ~ "dry wt")),
     xlab = expression("Concentration Cl" ~ (mu ~ moles ~ g^{-1} ~ "dry wt")))

but note there is no need to paste strings and other features here.

Both produce:

Note the issue plotmath has with the superscript 2. You may wish to add some extra space for the y-axis margin to accommodate that:

op <- par(mar = c(5,4.5,4,2) + 0.1)
plot(y ~ x, data = df,
     ylab = expression("Average Conc of S- on plates" ~
                          (mu ~ moles ~ cm^{-2} ~ "dry wt")),
     xlab = expression("Concentration Cl" ~ (mu ~ moles ~ g^{-1} ~ "dry wt")))
par(op)

producing

Superscripts within ggplot2's axis text

This can be done with functions scale_x_log2 and scale_y_log2 that can be found in GitHub package jrnoldmisc.

First, install the package.

devtools::install_github("jrnold/rubbish")

Then, coerce the variables to numeric. I wil work with a copy of the original dataframe.

df1 <- df
df1[] <- lapply(df1, function(x){
  x <- as.character(x)
  sapply(x, function(.x)eval(parse(text = .x)))
})

Now, graph it.

library(jrnoldmisc)
library(ggplot2)
library(MASS)
library(scales)

a <- ggplot(df1, aes(x = x, y = y, size = 4)) + 
  geom_point(show.legend = FALSE) +
  scale_x_log2(limits = c(0.01, NA), 
                labels = trans_format("log2", math_format(2^.x)),
                breaks = trans_breaks("log2", function(x) 2^x, n = 10)) +
  scale_y_log2(limits = c(0.01, NA),
                labels = trans_format("log2", math_format(2^.x)),
                breaks = trans_breaks("log2", function(x) 2^x, n = 10))
a + annotation_logticks(base = 2)

Edit.

Following the discussion in the comments, here are the two other ways that were seen to give different axis labels.

1. Axis labels every tick mark. Set limits = c(1.01, NA) and function argument n = 11, an odd number.
2. Axis labels on odd number exponents. Keep limits = c(0.01, NA), change to function(x) 2^(x - 1), n = 11.

Just the instructions, no plots.

The first.

a <- ggplot(df1, aes(x = x, y = y, size = 4)) + 
  geom_point(show.legend = FALSE) +
  scale_x_log2(limits = c(1.01, NA), 
                labels = trans_format("log2", math_format(2^.x)),
                breaks = trans_breaks("log2", function(x) 2^(x), n = 11)) +
  scale_y_log2(limits = c(1.01, NA),
                labels = trans_format("log2", math_format(2^.x)),
                breaks = trans_breaks("log2", function(x) 2^(x), n = 11))
a + annotation_logticks(base = 2)

And the second.

a <- ggplot(df1, aes(x = x, y = y, size = 4)) + 
  geom_point(show.legend = FALSE) +
  scale_x_log2(limits = c(0.01, NA), 
               labels = trans_format("log2", math_format(2^.x)),
               breaks = trans_breaks("log2", function(x) 2^(x - 1), n = 11)) +
  scale_y_log2(limits = c(0.01, NA),
               labels = trans_format("log2", math_format(2^.x)),
               breaks = trans_breaks("log2", function(x) 2^(x - 1), n = 11))
a + annotation_logticks(base = 2)

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