Important modifications to be applied the Bookdown of Workshop 7

Please read through the presenter and developer protocol for help with the GitHub workflow. For RMarkdown help, refer to our book template. R Markdown: The Definitive Guide is also a very helpful resource, and covers the tasks outlined below, including how to preview the book locally while you work.

[x] Ensure that the material matches the presentation. The first priority for the book is that it matches any changes made to the presentation. The bookdown can and should have extra text so that participants can work through the material without help (i.e. the extra text should essentially fill the spot of a presenter, consider taking material from the presenter notes and adding it here).
[x] Match code chunks to the presentation. Verify that all code shown in the presentation is present in the RMarkdown version. It is particularly important for the exercises (or challenges) to match the challenges in the presentations.
[x] Add supporting images from the presentation to the RMarkdown (if they are missing). These images include any image that is not coded in the presentations, including diagrams to explain contents or methods in greater detail.
[x] Verify the code. Verify that the code chunks work, and that relevant outputs (tables, figures, etc.) are being shown correctly in the book.
[x] Verify the writing. Reading through the text to improve the grammar and syntax is greatly appreciated.
[x] Ensure that both versions of the book match. Both languages should have identical books.

QCBSRworkshops / workshop07