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Factors and how to create them
Working with factors
9. Factors and NA values
Modifying factor variables
Summary

## Instruction

Often, there are missing values in our data (e.g., people don't answer every question in a survey). The problem with NAs is that some R functions won't include NA values at all in their result.

How can we inform R that we want to know about the missing information? We can use the fct_explicit_na() function, which adds a new level (named "(Missing)") and changes NA values to that level.

Let's change the NA values in the age column:

survey$age <- fct_explicit_na(survey$age)

## Exercise

Use fct_explicit_na() on the mrt_status column from survey. Assign the result to the same column.

### Stuck? Here's a hint!

Type:

survey$mrt_status <- fct_explicit_na(survey$mrt_status)