The **rowSums()** function in R can be used to calculate the sum of the values in each row of a matrix or data frame in R.

This function uses the following basic syntax:

**rowSums(x, na.rm=FALSE)**

where:

**x**: Name of the matrix or data frame.**na.rm**: Whether to ignore NA values. Default is FALSE.

The following examples show how to use this function in practice.

**Example 1: Use rowSums() with Data Frame**

The following code shows how to use **rowSums()** to find the sum of the values in each row of a data frame:

#create data frame df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, 2, 5, 3, 2), var3=c(3, 3, 6, 6, 8), var4=c(1, 1, 2, 14, 9)) #view data frame df var1 var2 var3 var4 1 1 7 3 1 2 3 2 3 1 3 3 5 6 2 4 4 3 6 14 5 5 2 8 9 #find sum of each row rowSums(df) [1] 12 9 16 27 24

**Example 2: Use rowSums() with NA Values in Data Frame**

The following code shows how to use **rowSums()** to find the sum of the values in each row of a data frame when there are NA values in some rows:

#create data frame with some NA values df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, NA, NA, 3, 2), var3=c(3, 3, 6, 6, 8), var4=c(1, 1, 2, NA, 9)) #view data frame df var1 var2 var3 var4 1 1 7 3 1 2 3 NA 3 1 3 3 NA 6 2 4 4 3 6 NA 5 5 2 8 9 #find sum of each row rowSums(df, na.rm=TRUE) [1] 12 7 11 13 24

**Example 3: Use rowSums() with Specific Rows**

The following code shows how to use **rowSums()** to find the sum of the values in specific rows of a data frame:

#create data frame with some NA values df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, NA, NA, 3, 2), var3=c(3, 3, 6, 6, 8), var4=c(1, 1, 2, NA, 9)) #view data frame df var1 var2 var3 var4 1 1 7 3 1 2 3 NA 3 1 3 3 NA 6 2 4 4 3 6 NA 5 5 2 8 9 #find sum of rows 1, 3, and 5 rowSums(df[c(1, 3, 5), ], na.rm=TRUE) 1 3 5 12 11 24

**Additional Resources**

How to Sum Specific Columns in R (With Examples)

How to Sum Specific Rows in R (With Examples)