Hybrid version of max(NA_real_, na.rm = TRUE) returns NA

[krlmlr]

data_frame(a = NA_real_) %>% summarise(a = max(a, na.rm = TRUE))
## # A tibble: 1 × 1
##       a
##   <dbl>
## 1    NA

[krlmlr]

@hadley: I wonder what the behavior of the following should be:

data_frame(a = NA_integer_) %>% summarise(a = max(a, na.rm = TRUE))
data_frame(a = integer()) %>% summarise(a = max(a))

Current code sets a to NA_integer_. It would be more consistent with base R to return -Inf instead, but this requires promoting to numeric.

[hadley]

Does base R always return a numeric? That might be a consistent principle. What does/should max(NA) return?

[krlmlr]

max(int_arg) returns an integer in base R.

The hybrid version of max(NA_integer_) returns NA_integer_, with both na.rm = TRUE or = FALSE.