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)
Use fct_explicit_na() on the mrt_status column from survey. Assign the result to the same column.
Type:
survey$mrt_status <- fct_explicit_na(survey$mrt_status)
