r语言 - 在一个列找到独特的价值观-值向量

Question

我想找到列的唯一值，但拿走指定向量中的值。在下面的示例数据中，我想从列all_areas减去向量area1和area2中的值中找到唯一的值。即结果应该是"城镇"、"城市"、"村庄">

set.seed(1)
area_df = data.frame(all_areas = sample(rep(c("foo", "bar", "big", "small", "town", "city", "village"),5),20),
number =  sample(1:100, 20))
area1 = c("foo", "bar")
area2 = c("big", "small")

Answer 1

您可以使用函数setdiff来查找all_areas与area1和area2之间的集合差值:

setdiff(area_df$all_areas, c(area1, area2))
[1] "city" "village" "town"   

Answer 2

我们可以使用%in%创建一个逻辑向量，将'all_areas'中的其他元素(!)否定到subset，然后使用unique返回唯一的行

unique(subset(area_df, !all_areas %in% c(area1, area2)))

与产出

all_areas number
5    village     44
7       city     33
8       town     84
9       city     35
10   village     70
11      town     74
16   village     87
19      town     40
20   village     93

Answer 3

使用dplyr方法:

library(dplyr)
area_df %>% 
filter(!all_areas %in% c(area1, area2)) %>% 
distinct
#>   all_areas number
#> 1   village     44
#> 2      city     33
#> 3      town     84
#> 4      city     35
#> 5   village     70
#> 6      town     74
#> 7   village     87
#> 8      town     40
#> 9   village     93