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

R ProgrammingServer Side ProgrammingProgramming

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

Live Demo

Consider the below data frame −

x1<−rpois(20,2)
x2<−rpois(20,2)
df1<−data.frame(x1,x2)
df1

## Output

x1 x2
1 4 3
2 3 3
3 3 0
4 3 0
5 2 0
6 2 0
7 0 4
8 1 1
9 4 3
10 0 1
11 3 2
12 5 3
13 1 1
14 3 2
15 1 3
16 2 2
17 3 1
18 1 1
19 5 1
20 3 1

## Example

library(data.table)

Finding the duplicate rows −

## Example

setDT(df1)[,list(Count=.N),names(df1)]

## Output

  x1 x2 Count
1:  4  3 2
2:  3  3 1
3:  3  0 2
4:  2  0 2
5:  0  4 1
6:  1  1 3
7:  0  1 1
8:  3  2 2
9:  5  3 1
10: 1  3 1
11: 2  2 1
12: 3  1 2
13: 5  1 1

## Example2

Live Demo

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
Updated on 09-Feb-2021 11:43:02