Week 1 Quiz:R Programming(Data Science Specialization):Answers2025

Q1 — R’s language origin

👉 R is a dialect of the S language developed at Bell Labs (not Lisp or Scheme).
🧩 Concept: R inherited syntax & semantics from S; it’s not a Lisp dialect.

Q2 — “Free software” freedoms

The four freedoms (0–3) are:
0️⃣ Run program for any purpose
1️⃣ Study how it works, modify it
2️⃣ Redistribute copies
3️⃣ Improve and share improvements
❌ Not included: restricting source code, limiting user purposes.

Q3 — Atomic data types

Atomic = single data type elements: numeric, integer, logical, complex, character.
❌ Not atomic: list, table, matrix, data.frame, array (composite types).

Q4 — x <- 4L

Suffix L makes integer literal.
✔️ class(x) → "integer"

Q5 — x <- c(4, TRUE)

R coerces mixed types → numeric dominates.
✔️ Output class: "numeric"

Q6 — rbind(x, y)

Combines vectors row-wise.
x & y each length 3 → 2 rows × 3 cols.
✔️ Shape: 2 × 3 matrix.

Q7 — Vector property

All elements must be same class.
✔️ Homogeneous type constraint.

Q8 — x <- list(2, "a", "b", TRUE) → x[[2]]

[[2]] extracts 2nd element directly.
✔️ Returns "a" (character vector length 1).

Q9 — Vector recycling

x = 1:4, y = 2:3 → shorter vector repeated:
(1+2, 2+3, 3+2, 4+3) = 3,5,5,7
✔️ Recycled addition; warning may occur.

Q10 — Set elements <6 to 0

Syntax: x[x < 6] <- 0
✔️ That’s the valid way; several incorrect variations shown.

Q11 — Dataset column names

From airquality dataset:
✔️ Ozone, Solar.R, Wind, Temp, Month, Day

Q12 — First two rows

Use head(airquality, 2) →

Q13 — Number of observations

nrow(airquality) → 153

Q14 — Last two rows

tail(airquality, 2) →

Q15 — Ozone value in 47th row

airquality[47, "Ozone"] → 21

Q16 — Missing values in Ozone

sum(is.na(airquality$Ozone)) → 37

Q17 — Mean Ozone (excluding NAs)

mean(airquality$Ozone, na.rm=TRUE) → ≈ 42.1

Q18 — Mean Solar.R where Ozone >31 & Temp >90

→ ≈ 212.8

Q19 — Mean Temp when Month==6

→ ≈ 79.1

Q20 — Max Ozone in May (Month==5)

→ 97

💡 Bonus: Useful Commands Recap