For these exercises we will use the US murders dataset again. Make sure you load it prior to starting.

library(dslabs)
data("murders")

You can create a data frame using the data.frame function. Here is a quick example:

temp <- c(35, 88, 42, 84, 81, 30)
city <- c("Beijing", "Lagos", "Paris", "Rio de Janeiro", 
          "San Juan", "Toronto")
city_temps <- data.frame(name = city, temperature = temp)

5. Use the rank function to determine the population rank of each state from smallest population size to biggest. Save these ranks in an object called ranks, then create a data frame with the state name and its rank. Call the data frame my_df and its 2 column respectively state and rank.

6. Repeat the previous exercise, but this time order the dataframe so that the states are ordered from least populous to most populous. Call the data frame my_df_ordered and its 2 column respectively state and rank.

Hint: create an object ind that stores the indexes needed to order the population values. Then use the bracket operator [ to re-order each column in the data frame.