A list holds heterogeneous objects—vectors, data frames, functions, even nested lists. Lists power JSON-like structures and model objects returned by lm().
Creating lists
item <- list(
name = "Ada",
scores = c(90, 92),
meta = list(source = "exam")
)
print(item$name)
print(length(item))List vs vector
Vectors are homogeneous atomic sequences; lists are recursive containers—similar to Python lists of mixed types.
Important interview questions and answers
- Q: How access list elements?
A: $name, [["name"]], or [[1]]—double brackets simplify structure. - Q: Why lm returns a list?
A: Complex results bundle coefficients, residuals, call, etc.
Self-check
- What function creates a list?
- How extract nested meta$source?
Tip: [[ ]] extracts one element; [ ] may return a sub-list.
Interview prep
- List indexing?
[[1]]or$nameextracts elements;[ ]may subset.