stat_density() error and bw.nrd() man file are in conflict on valid inputs

[mfoos]

Hello! This is relatively minor (in that it's easy for a novice to fix, though it's breaking to old code) but I think I am correct that it's in error. I was rerunning some old code that uses stat_density(..., bw = "SJ") and I got the error

Warning: Computation failed in stat_density(). Caused by error in precompute_bw(): ! bw must be one of "nrd0", "nrd", "ucv", "bcv", "sj", "sj-ste", or "sj-dpi", not "SJ". ℹ Did you mean "sj"?

And so I read the stat_density man page, which says bw should be set to:

The smoothing bandwidth to be used. If numeric, the standard deviation of the smoothing kernel. If character, a rule to choose the bandwidth, as listed in stats::bw.nrd(). Note that automatic calculation of the bandwidth does not take weights into account.

When you click into the stats manpage (https://stat.ethz.ch/R-manual/R-devel/library/stats/html/bandwidth.html) it shows several SJ options that one can use (bw.SJ, SJ-ste, SJ-dpi). But those are different from the ones in the ggplot2 error message, and indeed when you try them, they fail due to ggplot input checking (reprex below).

I'm not a bleeding-edge updater, but this is happening with R4.3.2 and ggplot2 3.5.1. I'm not in a position to update today, but the stats manpage linked above shows that in R4.5.0 their documentation has not changed. I also did not find any mention of this in the ggplot2 changelog.

library(ggplot2)

# Equivalent to legacy code that brought this to my attention
ggplot() +
  stat_density(data = diamonds, aes(x = x, fill = cut, alpha = .01), bw = "SJ")
#> Warning: Computation failed in `stat_density()`.
#> Caused by error in `precompute_bw()`:
#> ! `bw` must be one of "nrd0", "nrd", "ucv", "bcv", "sj", "sj-ste", or
#>   "sj-dpi", not "SJ".
#> ℹ Did you mean "sj"?

# Indicates "SJ" is still a valid bw value outside of stat_density/ggplot2
density(diamonds$x, bw = "SJ")
#> 
#> Call:
#>  density.default(x = diamonds$x, bw = "SJ")
#> 
#> Data: diamonds$x (53940 obs.);   Bandwidth 'bw' = 0.02009
#> 
#>        x                  y           
#>  Min.   :-0.06026   Min.   :0.000000  
#>  1st Qu.: 2.65487   1st Qu.:0.000000  
#>  Median : 5.37000   Median :0.001519  
#>  Mean   : 5.37000   Mean   :0.091983  
#>  3rd Qu.: 8.08513   3rd Qu.:0.141838  
#>  Max.   :10.80026   Max.   :0.763688

# Suggested by bandwidth manpage, but does not work
ggplot() +
  stat_density(data = diamonds, aes(x = x, fill = cut, alpha = .01), bw = "SJ-ste")
#> Warning: Computation failed in `stat_density()`.
#> Caused by error in `precompute_bw()`:
#> ! `bw` must be one of "nrd0", "nrd", "ucv", "bcv", "sj", "sj-ste", or
#>   "sj-dpi", not "SJ-ste".
#> ℹ Did you mean "sj-ste"?

# Suggested by bandwidth manpage, but does not work
ggplot() +
  stat_density(data = diamonds, aes(x = x, fill = cut, alpha = .01), bw = "bw.SJ")
#> Warning: Computation failed in `stat_density()`.
#> Caused by error in `precompute_bw()`:
#> ! `bw` must be one of "nrd0", "nrd", "ucv", "bcv", "sj", "sj-ste", or
#>   "sj-dpi", not "bw.SJ".

# ggplot error message answer does indeed work
ggplot() +
  stat_density(data = diamonds, aes(x = x, fill = cut, alpha = .01), bw = "sj-ste")

^{Created on 2024-06-12 with reprex v2.1.0}

[teunbrand]

The error message gives the valid options. Is the ask here to also allow uppercase, or is the ask here to change the documentation to list the options in full?

[mfoos]

Since the implementation still uses the bw.nrd (etc) code under the hood, and the desire is probably to continue to use that existing/precise/citation'd manpage for reference, I think allowing the uppercase options would be the more unifying solution.

[teunbrand]

The solution would be to use to_lower_ascii() before using arg_match0() in the piece of code below:

https://github.com/tidyverse/ggplot2/blob/2610840f7478af027294db0793df839199b8cb6b/R/stat-density.R#L245-L247