expressions as annotations broken

[robjhyndman]

I think this is due to the recent update. It used to work.

library(ggplot2)
ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point() +
  annotate("text", x = 3, y = 30, label = latex2exp::TeX("$\\alpha + \\beta x$"))
#> Error in `annotate()`:
#> ! Problem while setting up geom aesthetics.
#> ℹ Error occurred in the 2nd layer.
#> Caused by error in `list_sizes()` at ggplot2/R/geom-.R:518:3:
#> ! `x$label` must be a vector, not a <latexexpression/expression> object.

^{Created on 2025-09-18 with reprex v2.1.1}

[teunbrand]

Thanks for the report! The error message is correct, it should be a proper vector. Previously, the expressions were allowed by mistake. The parse argument should be used if the intent is to use an expression.

[robjhyndman]

OK, but the parse argument doesn't seem to make any difference.

[yutannihilation]

It seems latex2exp::TeX() can return characters by output = "character". It's a bit inconvenient, but I hope this works for you...

[robjhyndman]

Thanks. In case anyone else has the same problem, the solution was a combination of these suggestions:

library(ggplot2)

ggplot(mtcars, aes(x = wt, y = mpg)) +
  geom_point() +
  annotate(
    "text",
    x = 3,
    y = 30,
    label = latex2exp::TeX("$\\alpha + \\beta x$", output = "character"),
    parse = TRUE,
    size = 5
  )

^{Created on 2025-09-19 with reprex v2.1.1}

[RCinbo]

Does anyone have a solution for axis labels?

ggplot(mtcars, aes(x = wt, y = mpg)) +
    geom_point() +
    annotate(
        "text",
        x = 3,
        y = 30,
        label = latex2exp::TeX("$\\alpha + \\beta x$", output = "character"),
        parse = TRUE,
        size = 5
    ) +
    scale_x_continuous(breaks = 3, labels = TeX("$\\alpha$"))

yields

Error in vec_size():
! x must be a vector, not a <latexexpression/expression> object.

ggplot(mtcars, aes(x = wt, y = mpg)) +
    geom_point() +
    annotate(
        "text",
        x = 3,
        y = 30,
        label = latex2exp::TeX("$\\alpha + \\beta x$", output = "character"),
        parse = TRUE,
        size = 5
    ) +
    scale_x_continuous(breaks = 3, labels = TeX("$\\alpha$", output = character), parse = TRUE)

yields:
Error in scale_x_continuous(breaks = 3, labels = TeX("$\alpha$", output = character), :
unused argument (parse = TRUE)

[yutannihilation]

Thanks, confirmed. Could you file a new issue? It seems this is so tricky that I cannot immediately come up with a good fix.

The error happens here. key is a data frame containing a latexexpression object in .label column.

ggplot2/R/guide-.R

Line 287 in af6f4e8

key <- vec_slice(key, is.finite(oob_censor_any(breaks, range)))

The problem is, the latexexpression object cannot be subset by vec_slice() because

x <- as.list(latex2exp::TeX("$\\alpha$"))
vctrs::obj_is_vector(x)
#> [1] FALSE

However, it works if the object doesn't have S3 classes.

vctrs::obj_is_vector(unclass(x))
#> [1] TRUE

So, an easy workaround is to use unclass(). Or, you can simply use parse(text =) instead of latex2exp.

library(ggplot2)

ggplot(mtcars, aes(x = wt, y = mpg)) +
    geom_point() +
    annotate(
        "text",
        x = 3,
        y = 30,
        label = latex2exp::TeX("$\\alpha + \\beta x$", output = "character"),
        parse = TRUE,
        size = 5
    ) +
    scale_x_continuous(breaks = 3, labels = unclass(latex2exp::TeX("$\\alpha$")))

^{Created on 2025-09-23 with reprex v2.1.1}