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Square-root transforms happily inverse-transforms negative values #214
Description
I'm not sure if this should be fixed, but it does lead to some confusing behaviour (tidyverse/ggplot2#980):
library(scales)
trans <- sqrt_trans()
trans$inverse(-2)
#> [1] 4
trans$transform(4)
#> [1] 2
trans <- sqrt_trans()
trans$inverse(-2)
#> [1] 4
# this is what I would expect to happen
trans2 <- trans_new("sqrt2", sqrt, function(x) ifelse(x < 0, NA_real_, x^2), domain = c(0, Inf))
trans2$inverse(-2)
#> [1] NACreated on 2019-06-25 by the reprex package (v0.2.1)
Activity
hadley commentedon Nov 5, 2019
Reverting the fix because it causes a failure in ggplot2
zeehio commentedon Nov 19, 2019
I would expect something like
sign(x) * sqrt(abs(x))with a reverse transform likesign(x)*x^2.Edit: I just saw Hadley had the same idea on the ggplot2 issue
Edit2: I want to add that I would find a sqrt scale that handles negative values useful for visualization purposes regardless of the linked ggplot2 issue.
thomasp85 commentedon Nov 2, 2023
Changes in ggplot2 means we can now reapply the fix