Add description about arrang()ing NA

[yutannihilation]

(This is not related to the release of 0.8.0)

arrange() sorts NA to the end, whether the column is wrapped with desc() or not.

dplyr::arrange(data.frame(x = c(NA, 0, 1)), x)
#>    x
#> 1  0
#> 2  1
#> 3 NA
dplyr::arrange(data.frame(x = c(NA, 0, 1)), desc(x))
#>    x
#> 1  1
#> 2  0
#> 3 NA

^{Created on 2019-01-05 by the reprex package (v0.2.1)}

I guess this is intentional as the test case says so. I haven't seen someone complained about this behaviour, but I feel this is worth noting.

[romainfrancois]

Thanks.

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/