How to include NA data in a table

Question

I've recently been using the package tab in R to build frequency tables. Using the tabfreq() or the tabmulti() functions, the default output excludes NA values. Does anyone know the command to include NA values within these functions?

Answer 1

The table() function in base R can display missing values (i.e. NAs) via useNA, which takes several arguments: "no", "ifany", or "always".

data(airquality) # loads the built-in data frame, which has NAs
table(airquality$Ozone, useNA = "always") # always displays the number of missing values
table(airquality$Wind, useNA = "ifany") # only displays the number of missing values if there are some