You can use the **is.na()** function in R to check for missing values in vectors and data frames.

#check if each individual value is NA is.na(x) #count total NA values sum(is.na(x)) #identify positions of NA values which(is.na(x))

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

**Example 1: Use is.na() with Vectors**

The following code shows how to use the **is.na()** function to check for missing values in a vector:

#define vector with some missing values x <- c(3, 5, 5, NA, 7, NA, 12, 16) #check if each individual value is NA is.na(x) [1] FALSE FALSE FALSE TRUE FALSE TRUE FALSE FALSE #count total NA values sum(is.na(x)) [1] 2 #identify positions of NA values which(is.na(x)) [1] 4 6

From the output we can see:

- There are 2 missing values in the vector.
- The missing values are located in position 4 and 6.

**Example 2: ****Use is.na() with Data Frames**

The following code shows how to use the is.na() function to check for missing values in a data frame:

#create data frame df <- data.frame(var1=c(1, 3, 3, 4, 5), var2=c(7, NA, NA, 3, 2), var3=c(3, 3, 6, NA, 8), var4=c(NA, 1, 2, 8, 9)) #view data frame df var1 var2 var3 var4 1 1 7 3 NA 2 3 NA 3 1 3 3 NA 6 2 4 4 3 NA 8 5 5 2 8 9 #find total NA values in data frame sum(is.na(df)) [1] 4 #find total NA values by column sapply(df, function(x) sum(is.na(x))) var1 var2 var3 var4 0 2 1 1

From the output we can see that there are **4** total NA values in the data frame.

We can also see:

- There are
**0**NA values in the ‘var1’ column. - There are
**2**NA values in the ‘var2’ column. - There are
**1**NA values in the ‘var3’ column. - There are
**1**NA values in the ‘var4’ column.

**Additional Resources**

The following tutorials explain other useful functions that can be used to handle missing values in R.

How to Use na.omit in R

How to Use na.rm in R

How to Impute Missing Values in R