Data wrangling

Question 1

What are the rows and columns called in a data frame?

Answer 1

Observations and variables, respectively.

Question 2

How can you see the number of rows and columns in a tibble when using the dplyr library

Answer 2

They are displayed at the top of the tibble when it is printed.

Question 3

Which dplyr verb allows you to look at a subset of observations based on a specific condition.

Answer 3

filter()

Ex: filter(my_tibble, country == “United States”)

Question 4

What is the syntax and definition of a pipe?

Answer 4

%>%

A pipe takes whatever is before it, and feeds it into the next step.

Question 5

Which dplyr verb sorts the observations in a dataset in ascending or descending order based on one of its variables?

Answer 5

arrange()

Ex: arrange(my_tibble, gdpPerCap)

Question 6

How can you arrange in descending order?

Answer 6

Add desc() around the variable you are arranging by.

Ex: my_tibble %>%
arrange(desc(gdpPerCap))

Question 7

Which dplyr verb allows you to change one of the variables in your dataset, or add a new variable?

Answer 7

mutate()

Ex: my_tibble %>%
mutate(pop = pop / 1000000)

Ex: my_tibble %>%
mutate(gdp = gdpPerCap * pop)