You can use the sum() function in R to find the sum of values in a vector.

This function uses the following basic syntax:

sum(x, na.rm=FALSE)

where:

• x: Name of the vector.
• na.rm: Whether to ignore NA values. Default is FALSE.

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

Example 1: Sum Values in Vector

The following code shows how to sum the values in a vector:

#create vector
x <- c(3, 6, 7, 12, 15)

#sum values in vector
sum(x)

[1] 43

If there happen to be NA values in the vector, you can use na.rm=TRUE to ignore the missing values when calculating the mean:

#create vector with some NA values
x <- c(3, NA, 7, NA, 15)

#sum values in vector
sum(x, na.rm=TRUE)

[1] 25

Example 2: Sum Values in Data Frame Column

The following code shows how to sum the values in a specific column of a data frame:

#create data frame
df <- data.frame(var1=c(1, 3, 3, 4, 5),
                 var2=c(7, 7, 8, 3, 2),
                 var3=c(3, 3, 6, 6, 8),
                 var4=c(1, 1, 2, 8, 9))

#view data frame
df

  var1 var2 var3 var4
1    1    7    3    1
2    3    7    3    1
3    3    8    6    2
4    4    3    6    8
5    5    2    8    9

#sum values in 'var1' column
sum(df$var1)

[1] 16

Example 3: Sum Values in Several Data Frame Columns

The following code shows how to use the sapply() function to sum the values in several columns of a data frame:

#create data frame
df <- data.frame(var1=c(1, 3, 3, 4, 5),
                 var2=c(7, 7, 8, 3, 2),
                 var3=c(3, 3, 6, 6, 8),
                 var4=c(1, 1, 2, 8, 9))

#view data frame
df

  var1 var2 var3 var4
1    1    7    3    1
2    3    7    3    1
3    3    8    6    2
4    4    3    6    8
5    5    2    8    9

#sum values in 'var1' and 'var3' columns
sapply(df[ , c('var1', 'var3')], sum)

var1 var3 
  16   26