Sorting of Arrays in R Programming

Sorting of Arrays in details

A vector is a one-dimensional array, defined by a single length dimension. A vector can be created using the c() function by passing a list of values. Sorting can be done in either ascending or descending order. Before sorting, certain factors should be considered:

• Sorting order – Ascending or Descending.
• Sorting based on multiple criteria – If sorting involves multiple columns, specify the order.
• Handling missing and duplicate values – Decide whether to remove or replace them, considering the impact on the data.

Method 1: sort() function

The sort() function in R is used to sort a vector. By default, it sorts in increasing order. To sort in descending order, set the decreasing parameter to TRUE.

Syntax:

sort(vector_name, decreasing = TRUE)

Parameters:

• vector_name: The vector to be sorted.
• decreasing: A Boolean value that determines whether sorting should be in descending order.

Example 1: Sorting in Ascending Order

# Create a vector
numbers <- c(45, 12, 78, 23, 56, 89, 34)

# Sort in ascending order
sort(numbers)

Output:

[1] 12 23 34 45 56 78 89

Example 2: Sorting in Descending Order

# Sort in descending order
sort(numbers, decreasing = TRUE)

Output:

[1] 89 78 56 45 34 23 12

Method 2: order() function

To sort data frames, the order() function is used. It sorts the data based on the specified column. To sort in descending order, use a negative sign. Sorting can also be done with multiple criteria. If two values in a column are the same, a secondary column can be used for sorting (e.g., sorting names alphabetically when ages are the same).

Example: Sorting a Data Frame by Age

# Define a data frame
students <- data.frame("Age" = c(20, 18, 22, 25, 19),
                       "Name" = c("Aria", "Leo", "Sophia", "Daniel", "Mia"))

# Sort the data frame based on the Age column
sorted_students <- students[order(students$Age), ]

# Print the sorted data frame
print(sorted_students)

Output:

Age    Name
2  18    Leo
5  19    Mia
1  20    Aria
3  22    Sophia
4  25    Daniel

Example 1: Sorting a Vector in Decreasing Order

# Define vector
numbers <- c(35, 10, 50, 25, 5, 40)

# Sort in decreasing order and return indices
order(-numbers)

Output:

[1] 3 6 1 4 2 5

Example 2: Sorting a Data Frame by Multiple Columns

# Define dataframe
students <- data.frame("Age" = c(14, 18, 14, 21, 18, 14),
                       "Name" = c("Liam", "Emma", "Noah",
                                  "Olivia", "Ava", "Sophia"))

# Sort the dataframe first by Age, then by Name
sorted_students <- students[order(students$Age, students$Name), ]

# Print sorted dataframe
print(sorted_students)

Output:

Age    Name
6   14  Sophia
3   14   Noah
1   14   Liam
5   18     Ava
2   18   Emma
4   21 Olivia

Method 3: Sorting an Array Using a Loop

# Create linear array
arr <- c(8, 3, 7, 2, 6, 5, 4, 1)

# Repeat until the array is sorted
repeat
{
    swapped <- FALSE

    # Iterate through the array
    for (i in 2:length(arr))
    {
        newArr <- arr
        if (arr[i - 1] > arr[i])
        {
            newArr[i - 1] <- arr[i]
            newArr[i] <- arr[i - 1]
            arr <- newArr
            swapped <- TRUE
        }
    }

    if (!swapped) {break}
}

# Print sorted array
print(arr)

Output:

[1] 1 2 3 4 5 6 7 8

Method 4: Using dplyr Package for Sorting

# Install and load dplyr package
install.packages("dplyr")
library(dplyr)

# Create dataframe
employees <- data.frame("Age" = c(30, 45, 28, 35, 40),
                        "Name" = c("David", "Alice", "Ethan",
                                   "Olivia", "Sophia"))

# Sort the dataframe by Age using arrange()
sorted_employees <- arrange(employees, Age)

# Print sorted dataframe
print(sorted_employees)

Output:

Age    Name
3   28   Ethan
1   30   David
4   35  Olivia
5   40  Sophia
2   45   Alice