How can I filter in R only those rows in data.frame in which the value for column V6 appears exactly 2 times.

I try:

library(dplyr)

df <- as.data.frame(date)
df1 <- subset(df,duplicated(V6))

CodePudding user response：

You can use the following code:

df[with(df, ave(V6, V6, FUN = length)) == 2,]

Output:

   V1 V6
5   4  5
7   6  9
8   7  9
12 11  5

Data used:

df <- data.frame(V1 = c(0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15),
                 V6 = c("V5", "3", "2", "3", "5", "8", "9", "9", "4", "3", "3", "5", "6", "6", "6", "7"))

CodePudding user response：

Something like this? Values 3 and 4 only appear once in V6, value 5 three times. So only rows having value of 1 in V6 were kept:

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union

data <- tibble(
  V1 = c(1,2,3,4,5,6,7),
  V6 = c(1,1,3,4,5,5,5)
)
data
#> # A tibble: 7 × 2
#>      V1    V6
#>   <dbl> <dbl>
#> 1     1     1
#> 2     2     1
#> 3     3     3
#> 4     4     4
#> 5     5     5
#> 6     6     5
#> 7     7     5

data %>%
  group_by(V6) %>%
  filter(n() == 2)
#> # A tibble: 2 × 2
#> # Groups:   V6 [1]
#>      V1    V6
#>   <dbl> <dbl>
#> 1     1     1
#> 2     2     1

^{Created on 2022-06-24 by the reprex package (v2.0.0)}