根据列中的反向条件删除行

Question

I have a large dataset for which this needs to be done but I will describe the problem for a smaller one.

Var1	Var2
A	B
A	C
A	D
B	A
E	F
G	H

I want to keep only one of the rows with values "AB" and drop the row with the reverse "BA". All the other rows should also remain.

Thanks in advance.

Answer 1

df[!(df$Var1 == 'B' & df$Var1 == 'A'), ]

With dplyr:

dplyr::filter(df, !(Var1 == 'B' & Var1 == 'A'))

Reproducible input data:

df <- data.frame(
  Var1 = c('A', 'A', 'A', 'B', 'E', 'G'),
  Var2 = c('B', 'C', 'D', 'A', 'F', 'H')
)

Answer 2

if I understand correctly

df <- df <- data.frame(
  Var1 = c('A', 'A', 'A', 'B', 'E', 'G'),
  Var2 = c('B', 'C', 'D', 'A', 'F', 'H')
)

fltr <- !duplicated(apply(df, 1, function(x) paste0(sort(x), collapse = "")))

df[fltr, ]
#>   Var1 Var2
#> 1    A    B
#> 2    A    C
#> 3    A    D
#> 5    E    F
#> 6    G    H

^{Created on 2022-01-11 by the reprex package (v2.0.1)}