Special characters and superscripts on plot axis titles

plot, plotmath, r, superscript

Solution

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

Problem

I am trying to make a y-axis title with both a special character and a superscript. I am able to do this, but I want the closing parentheses not to be superscripted. And that's what I'm having a problem with. I think its just a placing of my parenthesis, but I've tried (seemingly) everything. ``` plot(WatexCl, ConcuM, col = as.numeric(1), pch = as.numeric(Depth), xlab = expression(paste("Concentration Cl ( ", mu, "moles/g dry wt)")), ylab = expression(paste("Average Conc of S- on plates ( ", mu, "Moles/cm"^"2"),)), data = plates) ```

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