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   j

Finding the unique values in column x1 −

> unique(df[c("x1")]) x1 1 A 6 B 11 C 16 D

Finding the unique values in column x2 −

> unique(df[c("x2")]) x2 1 5 3 10 11 15 17 20

Finding the unique values in column x3 −

> unique(df[c("x3")]) x3 1 India 5 Russia 8 China 13 Indonesia 15 Iceland

Finding 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