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How to find the unique values in a column of an R data frame?
Categorical variables have multiple categories but if the data set is large and the categories are also large in numbers then it becomes a little difficult to recognize them. Therefore, we can extract unique values for categorical variables that will help us to easily recognize the categories of a categorical variable. We can do this by using unique for every column of an R data frame.
Example
Consider the below data frame −
> x1<-rep(c("A","B","C","D"),each=5)
> x2<-rep(c(5,10,15,20),times=c(2,8,6,4))
> x3<-rep(c("India","Russia","China","Indonesia","Iceland"),times=c(4,3,5,2,6))
> x4<-rep(c(letters[1:10]),times=2)
> df<-data.frame(x1,x2,x3,x4)
> df
x1 x2 x3 x4
1 A 5 India a
2 A 5 India b
3 A 10 India c
4 A 10 India d
5 A 10 Russia e
6 B 10 Russia f
7 B 10 Russia g
8 B 10 China h
9 B 10 China i
10 B 10 China j
11 C 15 China a
12 C 15 China b
13 C 15 Indonesia c
14 C 15 Indonesia d
15 C 15 Iceland e
16 D 15 Iceland f
17 D 20 Iceland g
18 D 20 Iceland h
19 D 20 Iceland i
20 D 20 Iceland jFinding the unique values in column x1 −
> unique(df[c("x1")])
x1
1 A
6 B
11 C
16 DFinding the unique values in column x2 −
> unique(df[c("x2")])
x2
1 5
3 10
11 15
17 20Finding the unique values in column x3 −
> unique(df[c("x3")])
x3
1 India
5 Russia
8 China
13 Indonesia
15 IcelandFinding the unique values in column x4 −
> unique(df[c("x4")])
x4
1 a
2 b
3 c
4 d
5 e
6 f
7 g
8 h
9 i
10 j
Updated on: 11-Aug-2020
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