R：提取一列中的唯一值与另一列中的值匹配

Question

I would like to print string from df1 if it does not exist in df2

df1 <- data.frame(One = c("userID1", "userID5", "userID9"))
df2 <- data.frame(Two = c("userID2", "userID4", "userID1", "userID7"))

I would like to print string from df1 if it does not exist in df2

Output <- data.frame(Two = c("userID5", "userID9"))

Thank you in advance.

Answer 1

You could use dplyr 's anti_join :

library(dplyr)

df1 <- data.frame(One = c("userID1", "userID5", "userID9"))
df2 <- data.frame(Two = c("userID2", "userID4", "userID1", "userID7"))

df1 %>% 
  anti_join(df2, by = c("One" = "Two"))

returns

      One
1 userID5
2 userID9

Answer 2

Or simply

df1 <- data.frame(One = c("userID1", "userID5", "userID9"))
df2 <- data.frame(Two = c("userID2", "userID4", "userID1", "userID7"))

library(dplyr, warn.conflicts = F)
df1 %>%
  filter(!One %in% df2$Two)
#>       One
#> 1 userID5
#> 2 userID9

^{Created on 2021-08-19 by the reprex package (v2.0.1)}

Answer 3

Using data.table

library(data.table)
setDT(df1)[!df2, on = .(One = Two)]
       One
1: userID5
2: userID9