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 cbind 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 here.
