Check for Duplicate Values in Data Frame Column in R

To check if a data frame column contains duplicate values, we can use duplicated function along with any. For example, if we have a data frame called df that contains a column ID then we can check whether ID contains duplicate values or not by using the command −

any(duplicated(df$ID))

Example1

Consider the below data frame −

 Live Demo

ID<-1:20
x<-rpois(20,1)
df1<-data.frame(ID,x)
df1

Output

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

Checking whether x contains any duplicate or not −

any(duplicated(df1$x))

[1] TRUE

Example2

 Live Demo

S.No<-1:20
y<-round(rnorm(20,5,3),1)
df2<-data.frame(S.No,y)
df2

Output

   S.No  y
1   1   5.1
2   2   5.8
3   3   4.4
4   4  10.1
5   5   3.3
6   6   6.1
7   7   4.8
8   8  12.6
9   9   6.4
10 10   8.7
11 11   1.5
12 12   2.5
13 13   2.1
14 14   8.7
15 15   5.5
16 16   2.0
17 17   2.1
18 18   5.5
19 19   5.4
20 20   3.4

Checking whether y contains any duplicate or not −

any(duplicated(df2$y))

[1] TRUE