There are many files in the folder. For example, there are two Rmd files for Exercise 2. I copy your first Rmd and then knit it to HTML myself. The way of presentation seems different in the first file and the pdf file.
The data exploration part is well organized. Your README file is also well organized.
I have learned the function 'unique' from you.
I think writing is tedious in a few cases. For instance, "Hmmm...that command returned the index...". You can easily avoid such languages. Adding a .md file might be interesting.
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