# Sum of Two or Multiple Data Frame Columns in R (2 Examples)

In this article youâ€™ll learn how to compute the sum across two or more columns of a data frame in the R programming language.

Letâ€™s dive into it!

## Example Data

The first step is to define some example data:

```data <- data.frame(x1 = 1:5,             # Create data frame
x2 = c(3, 1, 7, 4, 4),
x3 = 5:9,
x4 = c(7, 4, 6, 4, 9))
data                                     # Print data frame```

As you can see based on Table 1, our example data is a data frame consisting of five rows and four columns. All the variables are numeric.

## Example 1: Calculate Sum of Two Columns Using + Operator

In this example, Iâ€™ll explain how to get the sum across two columns of our data frame.

For this, we can use the + and the \$ operators as shown below:

```data\$x1 + data\$x2                        # Sum of two columns
# [1]  4  3 10  8  9```

After executing the previous R code, the result is shown in the RStudio console.

## Example 2: Calculate Sum of Multiple Columns Using rowSums() & c() Functions

It is also possible to return the sum of more than two variables. To efficiently calculate the sum of the rows of a data frame subset, we can use the rowSums function as shown below:

```rowSums(data[ , c("x1", "x2", "x4")])    # Sum of multiple columns
# [1] 11  7 16 12 18```

The result of the addition of the variables x1, x2, and x4 is shown in the RStudio console.

## Video, Further Resources & Summary

Do you want to learn more about sums and data frames in R? Then I recommend having a look at the following video of my YouTube channel. I show the R code of this tutorial in the video:

Also, you might read the other articles on this website.