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Vectors hold one type. Lists hold mixed types — they're R's heterogeneous container.

person <- list(name = "Ada", age = 36, hobbies = c("math", "engines"))
person$name              # "Ada"
person[["age"]]          # 36
person$hobbies[1]        # "math"

Note [[ ]] vs [ ]:

• person[["age"]] returns the value (36, an integer)
• person["age"] returns a list of length 1 (a sub-list)

Lists are how R handles heterogeneous returns. A lm() regression result is a list of coefficients, residuals, fitted values, etc.

Data frames (next lesson) are special lists where every element is a vector of equal length — a tabular structure.