The “levels” Function in R

• Package: Base R (no specific package required)

• Purpose: Extracts or sets the levels of a factor.

• General Class: Data Attribute

• Required Argument(s):

• For extraction, the factor whose levels are to be extracted.

• For setting levels, the factor and the new levels to be assigned.

• Notable Optional Arguments:

• For setting levels, you can use levels(x) <- new_levels syntax to set new levels directly.

• Example:

• # Example data for using the levels attribute
  colors <- c("Red", "Blue", "Green", "Red", "Green", "Blue")
  color_factor <- factor(colors, levels = c("Red", "Blue", "Green"))
  
  # Extract levels from the factor
  extracted_levels <- levels(color_factor)
  
  # Display the extracted levels
  print(extracted_levels)
  
  # Set new levels for the factor
  new_levels <- c("Green", "Blue", "Red")
  levels(color_factor) <- new_levels
  
  # Display the factor with updated levels
  print(color_factor)

• In this example, the levels function is used to extract the levels from a factor (color_factor). Later, the same function is used to set new levels for the factor. Note that the levels function is used as an attribute and applied to a factor object, rather than being a standalone function with arguments.