Solutions to the intermediate exercises of the session on basic object types.

BasicObjectTypes-Solutions.R

# Task 1: Intermediate exercises I===============

# Create a vector containing the numbers 2, 5, 2.4 and 11.
vec_task_1 <- c(2, 5, 2.4, 11)

# What is the type of this vector?
typeof(vec_task_1)

# Transform this vector into the type integer. What happens?
typeof(vec_task_1)
as.integer(vec_task_1) # Does not modify the original vector
typeof(vec_task_1)
vec_task_1_int <- as.integer(vec_task_1) # Modifies the original vector
typeof(vec_task_1_int)

# Do you think you can create a vector containing the following elements:
#  "2", "Hello", 4.0, and TRUE?
mixed_vec <- c("2", "Hello", 4.0, TRUE)
mixed_vec
# See the tutorial for an explanation of the underlying hierarchy and
#  why the type is as follows:
typeof(mixed_vec)

# Task 2: Intermediate exercises II==============
# Create a vector with the numbers from -2 to 19 (step size: 0.75)
seq_vec <- seq(-2, 19, by=0.75)
seq_vec

# Create an index vector for this first vector (note: an index vector is a 
#  vector with all possible indices of the original vector)
seq_vec_index <- seq_along(seq_vec)
seq_vec_index

# Compute the log of each element of the first vector using vectorisation.
#  Anything that draws your attention?
log(seq_vec)
#  Logs for negative values do not exist, so NaNs were added

# What happens if you concatenate vectors of different types using c()?
#  Can you derive a systematization?
v_double <- c(2.0, 3.8)
v_int <- c(1L, 3L)
v_char <- c("1", "99")
typeof(c(v_double, v_int))
typeof(c(v_char, v_int))
#  The concatenated vector is coerced into the type of the original vector
#   according to the standard type hierarchy


# Task 3: Intermediate exercises III=============
# Create a list that has three named elements: "A", "B", and "C"
# The element "A" should contain the square root of the 
#  numbers form -2 to 8 (step size: 1)
# The element "B" should contain the log of numbers between 2 and 4 
#  (step size: 0.5)
# The element "C" should contain letters from a1 to g7 
#  (hint: use the pre-defined vector letters and the function paste())

li_1 <- list(
  "A"=sqrt(seq(-2, 8, by=1)), 
  "B"=log(seq(2, 4, by=0.5)), 
  "C"=paste(letters[1:7], 1:7, sep = "")
)
li_1

# Recommendable:
a_element <- sqrt(seq(-2, 8, by=1))
b_element <- log(seq(2, 4, by=0.5))
c_element <- paste(letters[1:7], 1:7, sep = "")

li_1 <- list(
  "A"=a_element, 
  "B"=b_element, 
  "C"=c_element
)
li_1