My video picks up right after the lesson on reading data into R. I go over how to check the dimensions and structure of your data and how to subset it. My video went long but here it is.
I did the same lesson both weeks (which I apologize for, I should have made time to prepare something new). The first week they suggested using the dim() function more to reinforce how the dataframe was changing, so I incorporated that. Andrew mentioned that he really liked that I included that it is a good idea to put a space in the brackets when you want all the rows (or all the columns).