levels()
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Description

The levels() function comes with R and is part of the Base R {base} package.

We use this function to find the levels, aka ordered categories, of a factor variable. Any NA values will be ignored and will not be considered separate levels. If the provided value is not a factor type, the result will be NULL.

Conceptual Usage

levels(factor variable)

Examples

The examples below use the carnivores dataset. Learn more about this dataset with get_help("carnivores").

# Show the carnivores dataset
carnivores
## # A tibble: 9 × 4
##   name              genus        awake brainwt
##   <chr>             <fct>        <dbl>   <dbl>
## 1 Arctic fox        Vulpes        11.5  0.0445
## 2 Cheetah           Acinonyx      11.9 NA     
## 3 Dog               Canis         13.9  0.07  
## 4 Gray seal         Haliochoerus  17.8  0.325 
## 5 Jaguar            Panthera      13.6  0.157 
## 6 Lion              Panthera      10.5 NA     
## 7 Northern fur seal Callorhinus   15.3 NA     
## 8 Red fox           Vulpes        14.2  0.0504
## 9 Tiger             Panthera       8.2 NA


# Define a factor for the example from the character variable `carnivores$genus`
my_factor <- as.factor(carnivores$genus)

# Show levels (ordered categories) of the factor variable:
levels(my_factor)
## [1] "Acinonyx"     "Callorhinus"  "Canis"        "Haliochoerus" "Panthera"     "Vulpes"


# Trying to find the levels of a non-factor results in NULL
# carnivores$genus is a character column
levels(carnivores$genus)
## [1] "Acinonyx"     "Callorhinus"  "Canis"        "Haliochoerus" "Panthera"     "Vulpes"