In the first part of this analysis, I turned a short list of movies into a database that could be used to answer basic questions about the list’s contents. Now I’d like to broaden this analysis by combining the original list with additional outside information — a process called data enrichment.
First, I needed to find and process a new set of data. In this case, I chose a list of the Best Movies of All Time compiled by popular film review aggregator, Rotten Tomatoes because I thought it might include movies that were more popular with a general audience. The RT list ranks movies by their adjusted Tomatometer rating (as of mid-August 2015) and pulls out the top 100. I copied this list over to a spreadsheet and created fields for Rank, Film, Year, and Decade.
Once this information was ready, I used the name of the movie itself to join the RT list to the original BBC list. This approach, while perfectly reasonable, does come with a certain level of risk because the two sources do not always match perfectly (find a detailed discussion of merging heterogeneous data sources here). When that happens you often have to match the information manually. Can you spot the problems associated with each pair of names below?
|Best Movies (RT)||Greatest American Films (BBC)|
|Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb||Dr Strangelove|
|E.T. the Extra-Terrestrial||ET: The Extra-Terrestrial|
|It’s a Wonderful Life||It’s a Wonderful Life|
|One Flew Over the Cuckoo’s Nest||One Flew Over the Cuckoo’s Nest|
|Schindler’s List||Schindler’s List|
|The Godfather Part II||The Godfather Part II|
The first mismatch is pretty obvious because Rotten Tomatoes includes the full tagline for the movie Dr. Strangelove in the title while the BBC does not. However, there are also some subtle differences in punctuation (such as the period after the abbreviation of “doctor” in the first column) that would still cause problems during a join. These punctuation issues show up more clearly with the second item which has differences in both the abbreviation of “E.T.” and the inclusion of a colon in the BBC version of the title. It gets more subtle from there!
The next three movie titles all contain a contraction or a possessive noun but one source uses an apostrophe while the other uses a single quotation mark. (To make this problem even harder to spot, some web browsers render them both the same. Check the page source.). Finally, the last paired items look identical … except that the first listing of The Godfather Part II includes a trailing space. Pretty esoteric, I know, but that is life in the data world.
With the two data sources aligned, I then created my final enhanced database and explored the information using another pivot table.
The first thing I noticed when I compared the BBC list to the Rotten Tomatoes list is that they only had 22 films in common. This surprised me a little at first but it makes sense when you realize that the RT list is not limited to American films. It also seemed to support my initial instinct that the RT database would contain many more recent films due to its online format.
A quick look at the films by source and decade (above) shows a huge number of recent films in the RT listing (including one, Mad Max: Fury Road, that was still in theaters when I first downloaded the data). It is also interesting to note that the spike in “best” movies for Rotten Tomatoes occurs in the 1950s instead of the 1970s. However, the large number of foreign films in the RT list for the 1950s leads quickly to discussions of Japan’s “Golden Age” of cinema during that time period.
Another interesting view of this information can be seen when you compare the two ranked lists side-by-side. The chart above shows the 22 films that appear on both lists with a line connecting their two ranks. This makes it easy to see where the sources agree and where they disagree. Several of the critical darlings (Citizen Kane, The Godfather, Singin’ in the Rain, and North by Northwest) also rank high on the RT list while others (many of them from the American New Wave period of the 1970s) show a drop in popularity. Meanwhile, other classically popular films like The Wizard of Oz and ET: The Extra-Terrestrial float upward.