Often you may want to compare two columns in R and write the results of the comparison to a third column.
You can easily do this by using the following syntax:
df$new_col <- ifelse(df$col1 > df$col2, 'A', ifelse(df$col1 < df$col2, 'B', 'C'))
This single line of code does the following:
- If column 1 is greater than column 2 then write ‘A’ as the output to the third column.
- Otherwise, if column 1 is less than column 2 then write ‘B’ as the output..
- Otherwise, write ‘C’ as the output.
The following example shows how to use this code in practice.
Example: Compare Two Columns in R
Suppose we have the following data frame that shows the number of goals scored by two soccer teams in five different matches:
#create data frame df <- data.frame(A_points=c(1, 3, 3, 3, 5), B_points=c(4, 5, 2, 3, 2)) #view data frame df A_points B_points 1 1 4 2 3 5 3 3 2 4 3 3 5 5 2
We can use the following code to compare the number of goals by row and output the winner of the match in a third column:
#compare A_points and B_points and output results to new column titled winner df$winner <- ifelse(df$A_points > df$B_points, 'A', ifelse(df$A_points < df$B_points, 'B', 'Tie')) #view data frame df A_points B_points winner 1 1 4 B 2 3 5 B 3 3 2 A 4 3 3 Tie 5 5 2 A
The results of the comparison are shown in the new column called winner.