*16*

You can use the argument **na.rm = TRUE** to exclude missing values when calculating descriptive statistics in R.

#calculate mean and exclude missing values mean(x, na.rm = TRUE) #calculate sum and exclude missing values sum(x, na.rm = TRUE) #calculate maximum and exclude missing values max(x, na.rm = TRUE) #calculate standard deviation and exclude missing values sd(x, na.rm = TRUE)

The following examples show how to use this argument in practice with both vectors and data frames.

**Example 1: Use na.rm with Vectors**

Suppose we attempt to calculate the mean, sum, max, and standard deviation for the following vector in R that contains some missing values:

#define vector with some missing values x

Each of these functions returns a value of **NA**.

To exclude missing values when performing these calculations, we can simply include the argument **na.rm = TRUE** as follows:

#define vector with some missing values x rm = TRUE) [1] 7.428571 sum(x, na.rm = TRUE) [1] 52 max(x, na.rm = TRUE) [1] 16 sd(x, na.rm = TRUE) [1] 4.790864

Notice that we were able to complete each calculation successfully while excluding the missing values.

**Example 2: Use na.rm with Data Frames**

Suppose we have the following data frame in R that contains some missing values:

#create data frame df frame(var1=c(1, 3, 3, 4, 5), var2=c(7, 7, NA, 3, 2), var3=c(3, 3, NA, 6, 8), var4=c(1, 1, 2, 8, NA)) #view data frame df var1 var2 var3 var4 1 1 7 3 1 2 3 7 3 1 3 3 NA NA 2 4 4 3 6 8 5 5 2 8 NA

We can use the **apply()** function to calculate descriptive statistics for each column in the data frame and use the **na.rm = TRUE** argument to exclude missing values when performing these calculations:

#calculate mean of each column apply(df, 2, mean, na.rm = TRUE) var1 var2 var3 var4 3.20 4.75 5.00 3.00 #calculate sum of each column apply(df, 2, sum, na.rm = TRUE) var1 var2 var3 var4 16 19 20 12 #calculate max of each column apply(df, 2, max, na.rm = TRUE) var1 var2 var3 var4 5 7 8 8 #calculate standard deviation of each column apply(df, 2, sd, na.rm = TRUE) var1 var2 var3 var4 1.483240 2.629956 2.449490 3.366502

Once again, we were able to complete each calculation successfully while excluding the missing values.

**Additional Resources**

The following tutorials explain how to perform other common tasks with missing values in R:

How to Use is.null in R

How to Use na.omit in R

How to Use is.na in R