What Is Factor Data Type in R?


Scott Campbell

What Is Factor Data Type in R?

In R programming, the factor data type is used to categorize or group variables. It is particularly useful when working with categorical data that has a fixed number of distinct values or levels. Factors are created using the factor() function in R.

Creating Factors

To create a factor in R, you can use the factor() function. Let’s consider an example where we have a vector of colors:

colors <- c("red", "blue", "green", "red", "green")
factors_colors <- factor(colors)

In this example, we created a factor called factors_colors using the factor() function applied to the vector colors. The resulting factor will contain the unique values of colors and their corresponding integer codes.

Finding Levels and Labels

The levels of a factor represent its distinct values. You can retrieve them using the levels() function:


The output will display all the unique values present in the factor:

  • "blue"
  • "green"
  • "red"

The labels represent the integer codes associated with each level. You can access them by using the labels() function:


The output will show:

  • "1"
  • "2"
  • "3"
  • "1"
  • "2"

Ordering Levels

By default, the levels of a factor are ordered alphabetically. However, you can specify a custom order using the levels parameter in the factor() function. Let's consider an example:

sizes <- c("small", "medium", "large")
factor_sizes <- factor(sizes, levels = c("small", "medium", "large"))

In this case, we created a factor called factor_sizes. By specifying the levels parameter, we ensured that the levels will be in the order: small, medium, large.

Rename Levels

You can also rename the levels of a factor using the levels() function. Let's assume we have a factor called factors_sizes:

# Output:
# [1] small  medium large 
# Levels: small medium large

To rename the levels, you can use:

levels(factors_sizes) <- c("S", "M", "L")
# Output:
# [1] S M L
# Levels: S M L

The levels have been renamed to 'S', 'M', and 'L' respectively.


In summary, the factor data type in R allows you to categorize variables into distinct groups or levels. It is particularly useful when working with categorical data. You can create factors using the factor() function, find the levels and labels using the levels() and labels() functions, order levels using the levels parameter, and rename levels using the levels() function.

Using factors can greatly enhance your data analysis and visualization in R by providing a structured way to handle categorical variables.

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