R — Factors

Creating factors

# Basic factor
colors <- factor(c("red", "blue", "green", "red", "blue"))
print(colors)
print(levels(colors))

# Ordered factor
sizes <- factor(c("small", "medium", "large", "medium"),
                levels = c("small", "medium", "large"),
                ordered = TRUE)
print(sizes)

Factor operations

# Summary
colors <- factor(c("red", "blue", "green", "red", "blue", "red"))
summary(colors)

# Table
table(colors)

# Levels
levels(colors)
nlevels(colors)

Modifying factors

# Add level
levels(colors) <- c(levels(colors), "yellow")

# Rename levels
levels(colors) <- c("Red", "Blue", "Green")

# Reorder
colors <- factor(colors, levels = c("Green", "Red", "Blue"))

Factors in data frames

df <- data.frame(
  color = factor(c("red", "blue", "green")),
  size = factor(c("S", "M", "L"), levels = c("S", "M", "L"), ordered = TRUE)
)

str(df)
summary(df)

Using forcats

library(forcats)

# fct_reorder
df <- data.frame(
  category = factor(c("C", "A", "B", "A", "C")),
  value = c(10, 20, 15, 25, 12)
)
df$category <- fct_reorder(df$category, df$value)

# fct_lump
colors <- factor(c("red", "blue", "green", "red", "red", "blue", "other"))
fct_lump(colors, n = 2)

Mini Practice

Write R code that:

1. Creates an ordered factor
2. Uses summary on a factor
3. Modifies factor levels
4. Uses forcats for factor manipulation

Up Next

In the next lesson, you'll learn about Strings — working with text in R.