# Introduction to R Programming for Data Science Week 2 Answers

**Course Name: Introduction to R Programming for Data Science**

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**These are answers of Introduction to R Programming for Data Science Week 2**

### Practice Quiz

**Q1. What is the difference between the expression c(1, 2, 3, 4, 5) and the expression c(5:1)?**

a. They both produce a factor with five numbers but the first is in ascending order and the second is in descending order.

b. The two expressions produce the same result.

c. One produces a factor and the other produces a vector.

d. They both produce a vector with five numbers but the first is in ascending order and the second is in descending order.

**Answer: d. They both produce a vector with five numbers but the first is in ascending order and the second is in descending order.**

**Q2. 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]?**

a. [1] TRUE TRUE TRUE TRUE FALSE

b. [1] 25 35 40 50

c. [1] 25 35 40

d. [1] TRUE TRUE TRUE FALSE FALSE

**Answer: c. [1] 25 35 40**

**These are answers of Introduction to R Programming for Data Science Week 2**

**Q3. What is the main difference between a list and a vector?**

a. A list is a multi-dimensional array of values, while a vector is a single dimensional array of values.

b. A list can contain nominal or ordinal values, while a vector cannot.

c. It is not possible to add or remove items from a list, but you can do this with a vector.

d. A list can contain different types of data, while a vector may only contain one type of data.

**Answer: d. A list can contain different types of data, while a vector may only contain one type of data.**

**Q4. What are three types of data you can store in an array or matrix? Select three answers.**

a. Vectors

b. Integers

c. Numeric valus

d. Strings

**Answer: b, c, d**

**These are answers of Introduction to R Programming for Data Science Week 2**

**Q5. In a data frame, each column is represented by a _________________ of values of the same data type.**

a. Matrix

b. List

c. Variable

d. Vector

**Answer: d. Vector**

**These are answers of Introduction to R Programming for Data Science Week 2**

### Graded Quiz

**Q1. What is a nominal factor?**

a. A factor with any type or number of elements.

b. A factor with ordering.

c. A factor with no implied order.

d. A factor that contains numeric data.

**Answer: c. A factor with no implied order.**

**Q2. 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)?**

a. 40

b. 45

c. 35

d. 50

**Answer: b. 45**

**These are answers of Introduction to R Programming for Data Science Week 2**

**Q3. 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?**

a. employee[“age”] == 35

b. employee[age] <- 35

c. employee[“age”] <- 35

d. employee[age] = 35

**Answer: c. employee[“age”] <- 35**

**Q4. What is the main difference between a matrix and an array?**

a. A matrix can contain vectors, but an array can only contain strings, characters, or integers.

b. A matrix can be arranged by rows or columns, but an array is always arranged by columns.

c. A matrix can contain multiple types of data, but an array can only contain data of the same type.

d. A matrix must be two dimensional, but an array can be single, two dimensional, or more than two dimensional.

**Answer: d. A matrix must be two dimensional, but an array can be single, two dimensional, or more than two dimensional.**

**These are answers of Introduction to R Programming for Data Science Week 2**

**Q5. 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?**

a. employee[title]

b. employee.title

c. employee[[3]]

d. employee$title

**Answer: d. employee$title**

**These are answers of Introduction to R Programming for Data Science Week 2**

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**These are answers of Introduction to R Programming for Data Science Week 2**