Factors in R

Introduction

Factors are used to represent categorical data in R. They store values as discrete levels and are essential for statistical modeling.

Creating Factors

# Using factor()
gender <- factor(c("Male", "Female", "Male", "Female"))
gender

# With specified levels
education <- factor(c("BS", "MS", "PhD", "BS"), 
                   levels = c("HS", "BS", "MS", "PhD"))
education

# Ordered factors
rank <- factor(c("Junior", "Senior", "Mid", "Junior"),
               levels = c("Junior", "Mid", "Senior"),
               ordered = TRUE)
rank

Factor Functions

gender <- factor(c("Male", "Female", "Male"))

levels(gender)        # Get levels
nlevels(gender)       # Number of levels
table(gender)         # Frequency table
summary(gender)       # Summary

Modifying Factors

gender <- factor(c("Male", "Female", "Male"))

# Add levels
levels(gender) <- c("Male", "Female", "Other")

# Reorder levels
gender <- relevel(gender, ref = "Female")

# Convert to numeric
as.numeric(gender)

Summary

Factors are essential for categorical data in R. They enable proper statistical analysis and modeling.