Day 4 Activities

Exercises

1. Change the animals data frame to a tibble called animals_tb. Save the row names to a column called animal_names before turning it into a tibble.

2. Use ggplot2 to plot the animal names (x-axis) versus the speed of the animal (y-axis) in animals_tb using a scatterplot. Customize the plot to display as shown below.

3. We decide that our plot would look better with the animal names ordered from slowest to fastest. Using the animals_tb tibble, reorder the animals on the x-axis to start with the slowest animal on the left-hand side of the plot to the fastest animal on the right-hand side of the plot by completing the following steps:

   a. Use the arrange() function to order the rows by speed from slowest to fastest. Then use the pull() function to extract the animal_names column as a vector of character values. Save the new variable as names_ordered_by_speed.

   b. Turn the animal_names column of animals_tb into a factor and specify the levels as names_ordered_by_speed from slowest to fastest (output in part a). Note: this step is crucial, because ggplot2 uses factor as plotting order, instead of the order we observe in data frame.

   c. Re-plot the scatterplot with the animal names in order from slowest to fastest.

Note

If you are interested in exploring other ways to reorder a variable in ggplot2, refer to this post.

4. Save the plot as a PDF called animals_by_speed_scatterplot.pdf to the results folder.

5. Use the functions from the dplyr package to perform the following tasks:

a. Extract the rows of animals_tb tibble with color of gray or tan, order the rows based from slowest to fastest speed, and save to a variable called animals_gray_tan.

b. Save animals_gray_tan as a comma-separated value file called animals_tb_ordered.csv to the results folder.