Week 1 Quiz >> R Programming

Week 1 Quiz >> R Programming

1. R was developed by statisticians working at

• Microsoft
• Johns Hopkins University
• The University of Auckland
• Harvard University

2. The definition of free software consists of four freedoms (freedoms 0 through 3). Which of the following is NOT one of the freedoms that are part of the definition? Select all that apply.

• The freedom to run the program, for any purpose.
• The freedom to redistribute copies so you can help your neighbor.
• The freedom to prevent users from using the software for undesirable purposes.
• The freedom to improve the program, and release your improvements to the public, so that the whole community benefits.
• The freedom to sell the software for any price.
• The freedom to restrict access to the source code for the software.
• The freedom to study how the program works, and adapt it to your needs.

3. In R the following are all atomic data types EXCEPT: (Select all that apply)

• matrix
• complex
• data frame
• table
• list
• array
• numeric
• logical
• character
• integer

4. If I execute the expression x <- 4L in R, what is the class of the object `x’ as determined by the `class()’ function?

• character
• complex
• numeric
• integer
• matrix
• logical

5. What is the class of the object defined by x <- c(4, TRUE)?

• numeric
• integer
• matrix
• list
• character
• logical

6. If I have two vectors x <- c(1,3, 5) and y <- c(3, 2, 10), what is produced by the expression cbind(x, y)?

• a matrix with 2 columns and 3 rows
• a 2 by 3 matrix
• a vector of length 2
• a 2 by 2 matrix
• a vector of length 3
• a 3 by 3 matrix

7. A key property of vectors in R is that

• a vector cannot have have attributes like dimensions
• elements of a vector all must be of the same class
• elements of a vector can be of different classes
• the length of a vector must be less than 32,768
• elements of a vector can only be character or numeric

8. Suppose I have a list defined as x <- list(2, “a”, “b”, TRUE). What does x[[1]] give me? Select all that apply.

• a numeric vector of length 1.
• a list containing the number 2.
• a character vector containing the element “2”.
• a list containing the letter “a”.
• a numeric vector containing the element 2.

9. Suppose I have a vector x <- 1:4 and a vector y <- 2. What is produced by the expression x + y?

• an integer vector with elements 3, 2, 3, 6.
• a numeric vector with elements 3, 2, 3, 4.
• an integer vector with elements 3, 2, 3, 4.
• a numeric vector with elements 3, 4, 5, 6.
• a numeric vector with elements 3, 2, 3, 6.
• a numeric vector with elements 1, 2, 3, 6.

10. Suppose I have a vector x <- c(17, 14, 4, 5, 13, 12, 10) and I want to set all elements of this vector that are greater than 10 to be equal to 4. What R code achieves this? Select all that apply.

• x[x > 10] <- 4
• x[x >= 10] <- 4
• x[x >= 11] <- 4
• x[x == 4] > 10
• x[x == 10] <- 4
• x[x < 10] <- 4
• x[x > 4] <- 10
• x[x > 10] == 4

11. Use the Week 1 Quiz Data Set to answer questions 11-20.
In the dataset provided for this Quiz, what are the column names of the dataset?

• Month, Day, Temp, Wind
• Ozone, Solar.R, Wind
• Ozone, Solar.R, Wind, Temp, Month, Day
• 1, 2, 3, 4, 5, 6

12. Extract the first 2 rows of the data frame and print them to the console. What does the output look like?

Ozone Solar.R Wind Temp Month Day
 1    18     224 13.8   67     9  17
 2    NA     258  9.7   81     7  22

Ozone Solar.R Wind Temp Month Day
 1     9      24 10.9   71     9  14
 2    18     131  8.0   76     9  29

✅ Ozone Solar.R Wind Temp Month Day
 1    41     190  7.4   67     5   1
 2    36     118  8.0   72     5   2

Ozone Solar.R Wind Temp Month Day
 1     7      NA  6.9   74     5  11
 2    35     274 10.3   82     7  17

13. How many observations (i.e. rows) are in this data frame?

• 129
• 160
• 45
• 153

14. Extract the last 2 rows of the data frame and print them to the console. What does the output look like?

Ozone Solar.R Wind Temp Month Day
 152    31     244 10.9   78     8  19
 153    29     127  9.7   82     6   7

✅ Ozone Solar.R Wind Temp Month Day
 152    18     131  8.0   76     9  29
 153    20     223 11.5   68     9  30

Ozone Solar.R Wind Temp Month Day
 152    34     307 12.0   66     5  17
 153    13      27 10.3   76     9  18

Ozone Solar.R Wind Temp Month Day
 152    11      44  9.7   62     5  20
 153   108     223  8.0   85     7  25

15. What is the value of Ozone in the 47th row?

• 18
• 34
• 21
• 63

16. How many missing values are in the Ozone column of this data frame?

• 78
• 9
• 37
• 43

17. What is the mean of the Ozone column in this dataset? Exclude missing values (coded as NA) from this calculation.

• 53.2
• 31.5
• 42.1
• 18.0

18. Extract the subset of rows of the data frame where Ozone values are above 31 and Temp values are above 90. What is the mean of Solar.R in this subset?

• 334.0
• 185.9
• 205.0
• 212.8

19. What is the mean of “Temp” when “Month” is equal to 6?

• 75.3
• 90.2
• 79.1
• 85.6

20. What was the maximum ozone value in the month of May (i.e. Month is equal to 5)?

• 100
• 18
• 97
• 115