How to Find Unique Values and Sort Them in R

Finding and Sorting unique values is a common task in R for data cleaning, exploration, and analysis. In this article, we will explore different methods to find unique values and sort them in R Programming Language.

Using sort() with unique()

In this approach, we use the unique() function to find unique values in a vector and then use the sort() function to sort them.

sub <- c("MATH", "SCIENCE", "SCIENCE", "ENGLISH", "HINDI", "ENGLISH", "HINDI",
             "MATH","PHYSICS")

# Find unique values and sort them in ascending order
val <- sort(unique(sub))
print(val)

Output:

[1] "ENGLISH" "HINDI" "MATH" "PHYSICS" "SCIENCE"

Below are some of the ways by which we can find unique values and sort them sets in R

1. Using duplicated() and order()
2. Using table() for Frequency Counts
3. Using distinct() and arrange() from dplyr Package

Method 1: Using duplicated() and order()

In this approach we use duplicated() to find unique rows in a dataframe and order() to sort them based on a specific column.

df <- data.frame(
  CustomerID = c(101, 102, 103, 101, 104),
  Amount = c(50, 30, 20, 50, 40)
)
df

# Remove duplicate customers
unique <- df[!duplicated(df$CustomerID), ]

# Sort by customers ID
sort_df <- unique[order(unique$CustomerID), ]
print(sort_df)

Output:

CustomerID Amount
1 101 50
2 102 30
3 103 20
4 101 50
5 104 40
CustomerID Amount
1 101 50
2 102 30
3 103 20
5 104 40

Method 2: Using table() from Frequency Counts

In this approach we use table() to get the frequency counts of unique values, and then sort them using the sort() function.

food <- c("Pizza", "Burger", "Pizza", "Salad", "Pizza", "Burger",
                              "Salad", "Pizza", "Burger")

# Get frequency counts of unique preferences
pre <- table(food)

# Sort preferences by count
sort_pre <- sort(pre, decreasing = TRUE)
print(sort_pre)

Output:

food
Pizza Burger Salad
4 3 2

Method 3: Using distinct() and arrange() from dplyr Package

In this method we use functions like distinct() and arrange() from dplyr package to find unique values and sort them using arrange() function.

library(dplyr)

df <- data.frame(
  Name = c("Vipul", "Jayesh", "Pratham", "Vipul"),
  Age = c(25, 30, 25, 35)
)

# Find unique values and sort them
sort <- df %>% distinct(Name) %>% arrange(Name)
print(sort)

Output:

Name
1 Jayesh
2 Pratham
3 Vipul