pick mean fails with warning is not numeric

[kletts]

Just observed some strange behaviour when combining the dplyr::pick function with mean, which fails because of a is.numeric test in the base R function mean.

df <- tibble(
  x = c(3, 2, 2, 2, 1),
  y = c(0, 2, 1, 1, 4),
  z1 = c("a", "a", "a", "b", "a"),
  z2 = c("c", "d", "d", "a", "c")
)

Taking the sum is not an issue:

df %>% summarise(sum(pick(c(x,y))))

Taking the mean fails (returns only NA) with the warning:

df %>% summarise(mean(pick(c(x,y))))
# A tibble: 1 × 1
  `mean(pick(c(x, y)))`
                  <dbl>
1                    NA
Warning message:
There was 1 warning in `summarise()`.
ℹ In argument: `mean(pick(c(x, y)))`.
Caused by warning in `mean.default()`:
! argument is not numeric or logical: returning NA 

Thanks for a great package. Christian

[kletts]

I'll close this issue as I realised this doesn't have to do with pick, but my misunderstanding of how mean works: eg
df %>% summarise(mean(c(x,y))) works where df %>% summarise(mean(x,y)) doesn't.