Table of Contents
Adding a column to a data frame in R is a fairly straightforward process. First, you must create the new column name and assign it a data type. Then, you can use the cbind() or the add_column() function to add the column to the data frame. You can then use the data frame’s column names to reference the column when using functions or plotting the data. Finally, you can use the summary() or str() functions to verify that the column was added correctly.
There are three common ways to add a new column to a data frame in R:
1. Use the $ Operator
df$new <- c(3, 3, 6, 7, 8, 12)
2. Use Brackets
df['new'] <- c(3, 3, 6, 7, 8, 12)
3. Use Cbind
df_new <- cbind(df, new)
This tutorial provides examples of how to use each of these methods in practice using the following data frame:
#create data frame
df <- data.frame(a = c('A', 'B', 'C', 'D', 'E'),
b = c(45, 56, 54, 57, 59))
#view data frame
df
a b
1 A 45
2 B 56
3 C 54
4 D 57
5 E 59
Example 1: Use the $ Operator
The following code shows how to add a column to a data frame by using the $ operator:
#define new column to add
new <- c(3, 3, 6, 7, 8)
#add column called 'new'
df$new <- new
#view new data frame
df
a b new
1 A 45 3
2 B 56 3
3 C 54 6
4 D 57 7
5 E 59 8
Example 2: Use Brackets
The following code shows how to add a column to a data frame by using brackets:
#define new column to add
new <- c(3, 3, 6, 7, 8)
#add column called 'new'
df['new'] <- new
#view new data frame
df
a b new
1 A 45 3
2 B 56 3
3 C 54 6
4 D 57 7
5 E 59 8
Example 3: Use Cbind
The following code shows how to add a column to a data frame by using the function, which is short for column-bind:
#define new column to add
new <- c(3, 3, 6, 7, 8)
#add column called 'new'
df_new <- cbind(df, new)
#view new data frame
df_new
a b new
1 A 45 3
2 B 56 3
3 C 54 6
4 D 57 7
5 E 59 8
You can actually use the cbind function to add multiple new columns at once:
#define new columns to add
new1 <- c(3, 3, 6, 7, 8)
new2 <- c(13, 14, 16, 17, 20)
#add columns called 'new1' and 'new2'
df_new <- cbind(df, new1, new2)
#view new data frame
df_new
a b new1 new2
1 A 45 3 13
2 B 56 3 14
3 C 54 6 16
4 D 57 7 17
5 E 59 8 20
Bonus: Set Column Names
After adding one or more columns to a data frame, you can use the colnames() function to specify the column names of the new data frame:
#create data frame
df <- data.frame(a = c('A', 'B', 'C', 'D', 'E'),
b = c(45, 56, 54, 57, 59),
new1 = c(3, 3, 6, 7, 8),
new2 = c(13, 14, 16, 17, 20))
#view data frame
df
a b new1 new2
1 A 45 3 13
2 B 56 3 14
3 C 54 6 16
4 D 57 7 17
5 E 59 8 20
#specify column names
colnames(df) <- c('a', 'b', 'c', 'd')
#view data frame
df
a b c d
1 A 45 3 13
2 B 56 3 14
3 C 54 6 16
4 D 57 7 17
5 E 59 8 20
You can find more R tutorials .