introduction to r programming for data science coursera answers week 2

Practice Quiz

1. What is the difference between the expression c(1, 2, 3, 4, 5) and the expression c(5:1)?

  • One produces a factor and the other produces a vector.
  • They both produce a vector with five numbers but the first is in ascending order and the second is in descending order.
  • The two expressions produce the same result.
  • They both produce a factor with five numbers but the first is in ascending order and the second is in descending order.

2. Assume that the variable test_result contains the vector c(25, 35, 40, 50, 75). What is the result of the expression test_result[test_result < 50]?

  • [1] 25 35 40
  • [1] 25 35 40 50
  • [1] TRUE TRUE TRUE FALSE FALSE
  • [1] TRUE TRUE TRUE TRUE FALSE

3. What is the main difference between a list and a vector?

  • A list is a multi-dimensional array of values, while a vector is a single dimensional array of values.
  • It is not possible to add or remove items from a list, but you can do this with a vector.
  • A list can contain nominal or ordinal values, while a vector cannot.
  • A list can contain different types of data, while a vector may only contain one type of data.

4. What are three types of data you can store in an array or matrix? Select three answers.

  • Integers

  • Numeric valus

  • Strings

  • Vectors

 

5. In a data frame, each column is represented by a _________________ of values of the same data type.

  • Vector
  • Variable
  • List
  • Matrix

Graded Quiz

6. What is a nominal factor?

  • A factor with any type or number of elements.
  • A factor with ordering.
  • A factor with no implied order.
  • A factor that contains numeric data.

7. Assume that the variable test_result contains the vector c(25, 35, 40, 50, 75).What is the result of the expression mean(test_result)?

  • 50
  • 45
  • 40
  • 35

8. Assume you have variable called employee that contains the expression list(name = “Juan”, age = 30). What is the correct command to change the contents of the age item to 35?

  • employee[“age”] <- 35
  • employee[age] <- 35
  • employee[age] = 35
  • employee[“age”] == 35

9. What is the main difference between a matrix and an array?

  • A matrix can be arranged by rows or columns, but an array is always arranged by columns.
  • A matrix can contain vectors, but an array can only contain strings, characters, or integers.
  • A matrix must be two dimensional, but an array can be single, two dimensional, or more than two dimensional.
  • A matrix can contain multiple types of data, but an array can only contain data of the same type.

10. Assume that you have a data frame called employee that contains three variables: name, age, and title. If you want to return all the values in the title variable, what command should you use?

  • employee[title]
  • employee[[3]]
  • employee$title
  • employee.title

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