Factors in R

R's type for categorical data, ordered or not.

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

levels_of <- levels(sizes)
counts <- table(sizes)
codes <- as.integer(sizes)
is_big <- sizes > "small"

relabeled <- factor(sizes, labels = c("S", "M", "L"))
dropped <- droplevels(sizes[sizes != "medium"])

How it works

1. levels fixes the category order explicitly.
2. ordered = TRUE allows comparisons between levels.
3. table counts levels; droplevels removes unused ones.

Keywords and builtins used here

• c
• droplevels
• factor
• levels
• table

The run, in numbers

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Step 4 of 4 in Vectors & types, step 4 of 20 in Language basics.

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