How to Sort Data in R: A Complete Tutorial

R provides a different way to sort the data either in ascending or descending order; Data analysts and data scientists use order(), sort() and packages like dplyr to sort data depending upon the structure of the obtained data.

TL;DR

• Use sort() to directly sort a vector and return the sorted values
• Use order() to get the indices that would sort a vector—ideal for sorting data frames
• Use dplyr::arrange() for a modern, readable approach to sorting data frames
• Handle NA values with the na.last parameter (TRUE puts NAs at end, FALSE at beginning)
• Sort in descending order with decreasing = TRUE or by using a minus sign

order() can sort vector, matrix, and also a data frame can be sorted in ascending and descending order with its help, which is shown in the final section of this tutorial.

Syntax of order()

The sort() function

Before diving into order(), let's look at the simpler sort() function. While order() returns indices, sort() directly returns the sorted values:

# Create a vector
values <- c(4, 12, 6, 7, 2, 9, 5)

# sort() returns the sorted values directly
sort(values)

[1]  2  4  5  6  7  9 12

The key difference is that sort() gives you the actual sorted values, while order() gives you the positions. This makes order() more useful for sorting data frames, as we'll see later.

Syntax of order()

The syntax of order() is shown below:

order(x, decreasing = TRUE or FALSE, na.last = TRUE or FALSE, method = c("auto", "shell", "quick", "radix"))

The argument above in order() states that:

• x: data-frames, matrices, or vectors
• decreasing: boolean value; TRUE then sort in descending order or FALSE then sort in ascending order.
• na.last: boolean value;TRUE then NA indices are put at last or FALSE then NA indices are put first.
• method: sorting method to be used.

order() in R

Let's look at an example of order() in action.

The code below creates a vector y containing a list of numbers. I'll use order(y) to get the indices that would sort these numbers.

y <- c(4, 12, 6, 7, 2, 9, 5)
order(y)

The above code gives the following output:

5 1 7 3 4 6 2

Here the order() will sort the given numbers according to its index in the ascending order. Since number 2 is the smallest, which has an index as five and number 4 is index 1, and similarly, the process moves forward in the same pattern.

y <- c(4, 12, 6, 7, 2, 9, 5)
y[order(y)]

The above code gives the following output:

2 4 5 6 7 9 12

Here the indexing of order is done where the actual values are printed in the ascending order. The values are ordered according to the index using order() then after each value accessed using y[some-value].

Sorting vector using different parameters in order()

Let's look at an example where the datasets contain the value as symbol NA(Not available).

order(x,na.last=TRUE)

x <- c(8, 2, 4, 1, -4, NA, 46, 8, 9, 5, 3)
order(x, na.last = TRUE)

The above code gives the following output:

5 4 2 11 3 10 1 8 9 7 6

Here the order() will also sort the given list of numbers according to its index in the ascending order. Since NA is present, its index will be placed last, where 6 will be placed last because of na.last=TRUE.

order(x,na.last=FALSE)

order(x, na.last = FALSE)

The above code gives the following output:

6 5 4 2 11 3 10 1 8 9 7

Here the order() will also sort the given list of numbers according to its index in the ascending order.Since NA is present, its index, which is 6, will be placed first because of na.last=FALSE.

order(x,decreasing=TRUE,na.last=TRUE)

order(x, decreasing = TRUE, na.last = TRUE)

The above code gives the following output:

7 9 1 8 10 3 11 2 4 5 6

Here order() will sort a given list of numbers according to its index in the descending order because of decreasing=TRUE: 46. The largest is placed at index 7, and the other values are arranged in a decreasing manner. Since NA is present, index 6 will be placed last because of na.last=TRUE.

order(x,decreasing=FALSE,na.last=FALSE)

order(x, decreasing = FALSE, na.last = FALSE)

The above code gives the following output:

6 5 4 2 11 3 10 1 8 9 7

Here NA is present which index is 6 will be placed at first because of na.last=FALSE. order() will sort a given list of numbers according to its index in the ascending order because of decreasing=FALSE: -4, which is smallest placed at index 5, and the other values are arranged increasingly.