Doc: `scale_y_continous(transform = "asn")` badly/wrongly documented

[LGraz]

scale_y_continuous(transform = "asn") uses the arcsin transformation (c.f. transform_asn())

?scale_y_continuous() does not give any information further info about "asn"

Hadley's old book claims that "asn" refers to the $tanh$-function (c.f. https://bookdown.dongzhuoer.com/hadley/ggplot2-book/scale-transformation ). Note that it is only one of the only resoureces I found that document what "asn" does.

Suggestion:

• correct the book (if you guys have the power)
• indicate on the helppage ?scale_y_continuous() that asn is the arcsin (this wasnt clear to me, who studied mathematics ^^)

[teunbrand]

I don't think it is a 'plain' arcsin either. The transformation and its inverse are defined here:

https://github.com/r-lib/scales/blob/fda519e2ac0828048c24f3c2b254c2607f75ac5c/R/transform-numeric.R#L12-L13

The transformation itself is from the {scales} package and documented in ?scales::transform_asn(). If there is an issue with the documentation, you can file an issue here: https://github.com/r-lib/scales/issues.

The current book can be found here: https://ggplot2-book.org/scales-position#sec-scale-transformation. Issues with the book can be filed here: https://github.com/hadley/ggplot2-book/issues.

In any case, I think the documentation of ggplot2 suffices: the ?scale_y_continuous() docs points to the scales::transform_*() functions and to the 'Numeric position scales' chapter of the book. I doesn't in itself document the asn transformation. As I don't think there is anything to improve for ggplot2, I'll close this issue.