在 R 中使用 bquote 上标后的下标

Question

I am trying to plot a specific R-square metric, the R2 relative to the 1:1 line. Here are some code to generate data and a plot. (I realize I am only calculating standard r-squared here, but thats fine for the purposes of working out the code).

#generate data.
set.seed(1234)
x <- rnorm(100)
y <- x*0.7 + rnorm(100)
mod <- lm(y~x)

#develop rsq label.
rsq <- round(summary(mod)$r.squared, 2)
rsq.1.lab <- bquote(R^2 [1:1] == .(rsq))

#drop plot and rsq label.
plot(y ~ x)
mtext(rsq.1.lab, side = 3, line = -2, adj = 0.05)

The plot looks like this:

This is pretty close, but the subscript is actually relative to the superscript, rather than being relative to the letter R. How can I change this? Looking for solutions that use base R, ideally keeping bquote() .

Answer 1

Use { / } grouping:

rsq.1.lab <- bquote({R^2} [1:1] == .(rsq))

or

rsq.1.lab <- bquote({R [1:1]}^2 == .(rsq))

or even a somewhat ridiculous

rsq.1.lab <- bquote(R * atop(2, "1:1") == .(rsq))

though we can reduce the font size a little using

rsq.1.lab <- bquote(R * scriptstyle(atop(2, "1:1")) == .(rsq))

Much of this is suggested/documented in ?plotmath .