# Convert NA into Factor Level in R (Example) | addNA Function for Missing Data

This article explains how to **turn NA values into a new factor level using the addNA function** in the R programming language.

Table of contents:

Let’s start right away!

## Example Data

The following data will be used as basement for this R tutorial:

my_fac <- factor(c("a", "b", NA, "a", "c", NA)) # Create example factor my_fac # Print example factor # [1] a b <NA> a c <NA> # Levels: a b c |

my_fac <- factor(c("a", "b", NA, "a", "c", NA)) # Create example factor my_fac # Print example factor # [1] a b <NA> a c <NA> # Levels: a b c

The previous output of the RStudio console shows the structure of our example data: We have created a factor vector with the three factor levels a, b, and c. Furthermore, our factor contains some NA values (i.e. missing data).

## Example: Turn NA into Extra Factor Level Using addNA() Function

In this example, I’ll demonstrate how to convert NA values to a new factor level using the addNA function in R.

Consider the R code below:

my_fac_NA <- addNA(my_fac) # Apply addNA function my_fac_NA # Print updated factor # [1] a b <NA> a c <NA> # Levels: a b c <NA> |

my_fac_NA <- addNA(my_fac) # Apply addNA function my_fac_NA # Print updated factor # [1] a b <NA> a c <NA> # Levels: a b c <NA>

Have a look at the previous output: It shows NA as additional factor level.

## Video, Further Resources & Summary

Would you like to learn more about the application of the addNA function? Then you may watch the following video on my YouTube channel. I illustrate the examples of this article in the video.

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In addition, you may want to have a look at the related tutorials that I have published on this website. I have released numerous tutorials already:

- Convert Factor to Character Class
- na_if R Function of dplyr Package
- Convert Values in Column into Row Names of Data Frame
- Help – Warning: invalid factor level, NA generated
- Convert Factor to Dummy Indicator Variables for Every Level
- R Programming Overview

In this R programming tutorial you have learned how to **apply the addNA function**. If you have any additional questions, don’t hesitate to let me know in the comments section.

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