How to count the number of duplicate rows in an R data frame?

To count the number of duplicate rows in an R data frame, we would first need to convert the data frame into a data.table object by using setDT and then count the duplicates with Count function. For example, if we have a data frame called df then the duplicate rows will be counted by using the command − setDT(df)[,list(Count=.N),names(df)].

Example1

y1<−sample(0:2,20,replace=TRUE)
y2<−sample(0:2,20,replace=TRUE)
df2<−data.frame(y1,y2)
df2

Output

y1 y2
1 2 1
2 2 2
3 0 0
4 2 2
5 0 2
6 2 2
7 1 0
8 0 2
9 1 0
10 2 1
11 1 2
12 0 2
13 1 0
14 0 0
15 2 1
16 1 1
17 0 0
18 0 1
19 2 1
20 2 0

Finding the duplicate rows −

Example

setDT(df2)[,list(Count=.N),names(df2)]

Output

y1 y2 Count
1: 2 1 4
2: 2 2 3
3: 0 0 3
4: 0 2 3
5: 1 0 3
6: 1 2 1
7: 1 1 1
8: 0 1 1
9: 2 0 1