Table of Contents
The row.names attribute is a useful tool when sorting a data frame in R. It allows you to sort the data frame in ascending or descending order using the name of each row as the sorting criterion. This is useful when you need to sort the data frame by one or more of its columns, or even by a custom criterion such as a specific keyword. In this case, the sorting is done automatically based on the row.names attribute, making sorting data frames much easier and more convenient.
You can use the following two methods to sort a data frame in R by using the row.names attribute:
Method 1: Sort Using Character row.names
df[order(row.names(df)), ]
Method 2: Sort Using Numeric row.names
df[order(as.numeric(row.names(df))), ]
The following examples shows how to use each method in practice.
Example 1: Sort Data Frame Using Character row.names
Suppose we have the following data frame in R:
#create data frame
df <- data.frame(position=c('G', 'G', 'F', 'F', 'C'),
points=c(99, 90, 86, 88, 95),
assists=c(33, 28, 31, 39, 34),
rebounds=c(30, 28, 24, 24, 28))
#set row names of data frame
row.names(df) <- c('A', 'C', 'E', 'D', 'B')
#view data frame
df
position points assists rebounds
A G 99 33 30
C G 90 28 28
E F 86 31 24
D F 88 39 24
B C 95 34 28
We can use the following syntax to sort the rows of the data frame alphabetically using the row.names attribute:
#sort rows alphabetically using row.names
df[order(row.names(df)), ]
position points assists rebounds
A G 99 33 30
B C 95 34 28
C G 90 28 28
D F 88 39 24
E F 86 31 24
The rows are sorted from A to Z based on the row name value.
You can also use the decreasing=TRUE argument to sort from Z to A:
#sort rows from Z to A using row.names
df[order(row.names(df), decreasing=TRUE), ]
position points assists rebounds
E F 86 31 24
D F 88 39 24
C G 90 28 28
B C 95 34 28
A G 99 33 30
Example 2: Sort Data Frame Using Numeric row.names
Suppose we have the following data frame in R:
#create data frame
df <- data.frame(position=c('G', 'G', 'F', 'F', 'C'),
points=c(99, 90, 86, 88, 95),
assists=c(33, 28, 31, 39, 34),
rebounds=c(30, 28, 24, 24, 28))
#set row names of data frame
row.names(df) <- c(1, 100, 4, 12, 19)
#view data frame
df
position points assists rebounds
1 G 99 33 30
100 G 90 28 28
4 F 86 31 24
12 F 88 39 24
19 C 95 34 28
#sort by row names from smallest to largest
df[order(as.numeric(row.names(df))), ]
position points assists rebounds
1 G 99 33 30
4 F 86 31 24
12 F 88 39 24
19 C 95 34 28
100 G 90 28 28
We could also use decreasing=TRUE to sort from largest to smallest:
#sort by row names from largest to smallest
df[order(as.numeric(row.names(df)), decreasing=TRUE), ]
position points assists rebounds
100 G 90 28 28
19 C 95 34 28
12 F 88 39 24
4 F 86 31 24
1 G 99 33 30
The following tutorials explain how to perform other common operations in R: