Basic Operations: Exercises

Exercise 1

What does the function seq do?

• Repeats a value multiple times.
• Builds a sequence of values.
• Loads a SQL data base.
• It’s part of another package and therefore not loaded in Base R.

TipHint

Use the help function ?.

CautionSolution

• Repeats a value multiple times.
• Builds a sequence of values.
• Loads a SQL data base.
• It’s part of another package and therefore not loaded in R.

Exercise 2

Why does the following code not work? Correct it so it does.

c(1, 2, 3, 4, 5)
mean(num_vec)

TipHint

Does the object num_vec actually exist?

CautionSolution

The object num_vec hasn’t been assigned yet. So let’s do that:

num_vec <- c(1, 2, 3, 4, 5)
mean(num_vec)

[1] 3

Exercise 3

Build the following vector with as little code as possible:

vec_1 <- c(
  1.0,
  2.0,
  3.0,
  4.0,
  5.0,
  5.1,
  5.2,
  5.3,
  5.4,
  5.5,
  2.0,
  2.0,
  2.0,
  2.0,
  2.0,
  2.0,
  2.0,
  2.0
)

TipHint

Use seq() and rep(). You can also build consecutive sequences using :.

CautionSolution

vec_1 <- c(1:5, seq(from = 5, to = 5.5, by = 0.1), rep(x = 2, times = 8))
vec_1

 [1] 1.0 2.0 3.0 4.0 5.0 5.0 5.1 5.2 5.3 5.4 5.5 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0

Exercise 4

Find all of the elements in the vector vec_num that are either equal to 1000, or lie between sqrt(11) and log(1.001).

vec_num <- c(
  sqrt(100)^3,
  exp(-6),
  22.02 / 3 * sqrt(4^2) * 0.25,
  -120987 / (47621 * 1.3^4)
)

TipHint

You need to combine three logical statements. Go at it step by step: first find all elements in vec_num that are equal to 1000, and then add a comparison for the rest of the statement behind an | (“or”).

CautionSolution

vec_num == 1000 | (vec_num < sqrt(11) & vec_num > log(1.001))

[1]  TRUE  TRUE FALSE FALSE