R dplyr n_distinct 计算独特的组合

n_distinct(..., na.rm = FALSE)

x <- c(1, 1, 2, 2, 2)
n_distinct(x)
#> [1] 2

y <- c(3, 3, NA, 3, 3)
n_distinct(y)
#> [1] 2
n_distinct(y, na.rm = TRUE)
#> [1] 1

# Pairs (1, 3), (2, 3), and (2, NA) are distinct
n_distinct(x, y)
#> [1] 3

# (2, NA) is dropped, leaving 2 distinct combinations
n_distinct(x, y, na.rm = TRUE)
#> [1] 2

# Also works with data frames
n_distinct(data.frame(x, y))
#> [1] 3