label_log() generated function outputs expr instead of a character vector as documented

[ppreshant]

Hello! I am trying to use the label_ functions for plotting formatted numbers in geom_text() instead of the intended use in ggplot2 scales. But the output of label_log() is different from that of label_scientific() so I thought this could be improved upon to make consistent?

I had to use the deparse() function with a map_chr() call to make scale_log() work eventually..

Here's the outputs of the label_..() functions -

# returns expression (not string)
scales::label_log(digits = 1)(c(1, 10, 100))
#> expression(10^0, 10^1, 10^2)

# returns string vector as documented
scales::label_scientific(digits = 1)(c(1, 10, 100))
#> [1] "1e+00" "1e+01" "1e+02"

# showing the functional output
scales::label_log()
#> function (x) 
#> {
#>     if (length(x) == 0) {
#>         return(expression())
#>     }
#>     exponent <- format(log(x, base = base), digits = digits)
#>     text <- paste0(base, "^", exponent)
#>     ret <- parse_safe(text)
#>     ret[is.na(x)] <- NA
#>     ret
#> }
#> <bytecode: 0x0000021649f9b4b8>
#> <environment: 0x000002164d3b7290>

^{Created on 2024-07-31 with reprex v2.1.0}

Here's an example code to make the geom_text() which only works with label_scientific()

library(tidyverse)

# make simple test data 3 columns, 5 rows
b <- tibble::tibble(b1 = 1:5, b2 = 10^b1)

# with label_scientific
ggplot2::ggplot(b, 
       aes(x = b1, y = b2)) + 
  geom_point() + 
  geom_text(aes(label = scales::label_scientific(digits = 1)(b2)), vjust = -2)

# with label_log()  
ggplot(b, 
       aes(x = b1, y = b2)) + 
  geom_point() + 
  geom_text(aes(label = scales::label_log()(b2)), vjust = -2)
#> Don't know how to automatically pick scale for object of type <expression>.
#> Defaulting to continuous.
#> Error in `geom_text()`:
#> ! Problem while computing aesthetics.
#> ℹ Error occurred in the 2nd layer.
#> Caused by error in `compute_aesthetics()`:
#> ! Aesthetics are not valid data columns.
#> ✖ The following aesthetics are invalid:
#> ✖ `label = (scales::label_log())(b2)`
#> ℹ Did you mistype the name of a data column or forget to add `after_stat()`?

# I can fix it by mapping a deparse() function
ggplot(b, 
       aes(x = b1, y = b2)) + 
  geom_point() + 
  geom_text(aes(label = scales::label_log()(b2) %>% 
                  {map_chr(as.list(.), deparse)}
                  ), 
            vjust = -2)

^{Created on 2024-07-31 with reprex v2.1.0}

[ppreshant]

Summary - Use format_log() instead of label_log() for char output, for use in geom_text(parse = TRUE)
Source : comment in the pull request