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We can use the following syntax to sum specific rows of a data frame in R:

with(df, sum(column_1[column_2 == 'some value']))

This syntax finds the sum of the rows in column 1 in which column 2 is equal to some value, where the data frame is calledÂ **df**.

This tutorial provides several examples of how to use this function in practice with the following data frame:

#create data frame df points = c(4, 7, 8, 8, 8, 9, 12), rebounds = c(3, 3, 4, 4, 6, 7, 7)) #view data frame df team points rebounds 1 A 4 3 2 A 7 3 3 B 8 4 4 B 8 4 5 B 8 6 6 C 9 7 7 C 12 7

**Example 1: Sum Rows Based on the Value of One Column**

The following code shows how to find the sum of all rows in the points column where team is equal to C:

#find sum of points where team is equal to 'C' with(df, sum(points[team == 'C'])) [1] 21

And the following code shows how to find the sum of all rows in the rebounds column where the value in the points column is greater than 7:

#find sum of rebounds where points is greater than 7 with(df, sum(rebounds[points > 7])) [1] 28

**Example 2: Sum Rows Based on the Value of Multiple Columns**

The following code shows how to find the sum of the rows in the rebounds column where the value in the points column is less than 8 **or** the value in the team column is equal to C:

with(df, sum(rebounds[points | team == 'C'])) [1] 20

And the following code shows how to find the sum of the rows in the rebounds column where the value in the points column is less than 10 **and** the value in the team column is equal toÂ B:

with(df, sum(rebounds[points & team == 'B'])) [1] 14

**Additional Resources**

How to Arrange Rows in R

How to Remove Duplicate Rows in R

How to Remove Rows with Some or All NAs in R