根据第二个小标题中的值过滤小标题

Question

Given the following tibbles:

df1<- tibble(A = c(1:10), B=sample(c(21:30)))
df2<-tibble(A = c(1,2,4,6,7))

I want to create df3 which contains all the rows in which df1$A is found in df2$A. I've tried

df3<- df1 %>% filter(A == df2%A))

but this returns only 2 rows, because it is matching the rows, not searching for the values. My real data set is several thousand rows.

Thanks in advance!

Answer 1

library(tidyverse)
df1<- tibble(A = c(1:10), B=sample(c(21:30)))
df2<-tibble(A = c(1,2,4,6,7))
df1 %>% 
  filter(df1$A %in% df2$A)

Answer 2

The proper way to do this is to use a semi_join()

Eg,

library(tidyverse)
set.seed(123)
df1 <- tibble(A = c(1:10), B = sample(c(21:30)))
df2 <- tibble(A = c(1, 2, 4, 6, 7))

df3 <- semi_join(df1, df2, by = "A")
df3
#> # A tibble: 5 x 2
#>       A     B
#>   <int> <int>
#> 1     1    23
#> 2     2    30
#> 3     4    28
#> 4     6    29
#> 5     7    21

^{Created on 2020-05-06 by the reprex package (v0.3.0)}