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

 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

Loading data.table object −

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