You can use the following basic syntax to add a column to a data frame in R based on the values in other columns:
#add new column 'col3' with values based on columns 1 and 2 df$col3 <- with(df, ifelse(col1 > col2, value_if_true, value_if_false))
The following examples show how to use this syntax in practice.
Example 1: Add Character Column Based on Other Columns
The following code shows how to add a new character column based on the values in other columns of the data frame:
#create data frame
df <- data.frame(team=c('Mavs', 'Cavs', 'Spurs', 'Nets'),
scored=c(99, 90, 84, 96),
allowed=c(95, 80, 87, 95))
#view data frame
df
team scored allowed
1 Mavs 99 95
2 Cavs 90 80
3 Spurs 84 87
4 Nets 96 95
#add 'result' column based on values in 'scored' and 'allowed' columns
df$result <- with(df, ifelse(scored > allowed, 'Win', 'Loss'))
#view updated data frame
df
team scored allowed result
1 Mavs 99 95 Win
2 Cavs 90 80 Win
3 Spurs 84 87 Loss
4 Nets 96 95 Win
And the following code shows how to add a new character column that combines two ifelse() functions to produce three potential values in a new column:
#create data frame
df <- data.frame(team=c('Mavs', 'Cavs', 'Spurs', 'Nets'),
scored=c(99, 90, 84, 96),
allowed=c(95, 80, 87, 95))
#view data frame
df
team scored allowed
1 Mavs 99 95
2 Cavs 90 80
3 Spurs 84 87
4 Nets 96 95
#add 'quality' column based on values in 'scored' and 'allowed' columns
df$quality <- with(df, ifelse(scored > 95, 'great',
ifelse(scored > 85, 'good', 'bad')))
#view updated data frame
df
team scored allowed quality
1 Mavs 99 95 great
2 Cavs 90 80 good
3 Spurs 84 87 bad
4 Nets 96 95 great
Example 2: Add Numeric Column Based on Other Columns
The following code shows how to add a new numeric column to a data frame based on the values in other columns:
#create data frame
df <- data.frame(team=c('Mavs', 'Cavs', 'Spurs', 'Nets'),
scored=c(99, 90, 84, 96),
allowed=c(95, 80, 87, 95))
#view data frame
df
team scored allowed
1 Mavs 99 95
2 Cavs 90 80
3 Spurs 84 87
4 Nets 96 95
#add 'lower_score' column based on values in 'scored' and 'allowed' columns
df$lower_score <- with(df, ifelse(scored > allowed, allowed, scored))
#view updated data frame
df
team scored allowed lower_score
1 Mavs 99 95 95
2 Cavs 90 80 80
3 Spurs 84 87 84
4 Nets 96 95 95
Additional Resources
How to Add Columns to Data Frame in R
How to Add an Empty Column to a Data Frame in R
How to Add an Index Column to Data Frame in R