How to keep the true uniques row?

Question

Here an example of a matrix,

A	B	C
1	1	1
1	1	4
1	2	4
2	1	1
3	1	1
3	1	2

I would like extract only rows which are unique in A and B. I can't use unique, duplicate etc. because they retain always one of my duplicated row.

In final result I wish obtain:

A	B	C
1	2	4
2	1	1

How can I do it? Thank you

What do you mean by unique? Can you explain with the other rows are not retained? — Maël, Feb 28 '22 at 11:05
Please provide enough code so others can better understand or reproduce the problem. — Community, Feb 28 '22 at 11:10

score 1 · Accepted Answer · answered Feb 28 '22 at 11:34

1

Here are couple of options -

Base R -

cols <- c('A', 'B')
res <- df[!(duplicated(df[cols]) | duplicated(df[cols], fromLast = TRUE)), ]
res

#  A B C
#3 1 2 4
#4 2 1 1

dplyr -

library(dplyr)
df %>% group_by(A, B) %>% filter(n() == 1) %>% ungroup

# A tibble: 2 x 3
#      A     B     C
#  <int> <int> <int>
#1     1     2     4
#2     2     1     1

answered Feb 28 '22 at 11:34

Ronak Shah

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Oh, wow, I did not understand the question like that but that makes more sense ahah. Let's see what OP thinks! – Maël Feb 28 '22 at 11:39
Perfect the three solution worked, even if with the dplyr I have a duplication of the A and B column. Thank you. – Seraz Mar 02 '22 at 08:36

score 1 · Answer 2 · answered Feb 28 '22 at 11:35

data.table

df <- data.frame(
  A = c(1L, 1L, 1L, 2L, 3L, 3L),
  B = c(1L, 1L, 2L, 1L, 1L, 1L),
  C = c(1L, 4L, 4L, 1L, 1L, 2L)
)

library(data.table)
setDT(df)[, .SD[.N == 1], by = list(A, B)]
#>    A B C
#> 1: 1 2 4
#> 2: 2 1 1

^{Created on 2022-02-28 by the reprex package (v2.0.1)}

How to keep the true uniques row?

2 Answers2