使用dplyr获取列的值

Question

我想让dplyr返回一个字符向量而不是数据帧.是否有捷径可寻？

#example data frame 
df <- data.frame( x=c('a','b','c','d','e','f','g','h'), 
                  y=c('a','a','b','b','c','c','d','d'),
                  z=c('a','a','a','a','a','a','d','d'),
                  stringsAsFactors = FALSE)


#desired output
unique(df$z)
[1] "a" "d"

#dplys's output
df %>% 
  select(z) %>%
  unique() 

z
1 a
7 d

Answer 1

尝试

library(dplyr)
df %>%
   select(z) %>%
   unique() %>% 
   .$z
#[1] "a" "d"

或使用 magrittr

library(magrittr)
df %>%
  select(z) %>%
  unique() %>%
  use_series(z)
#[1] "a" "d"