In earlier posts, I used the statistical software R to plot the trends in league average run scoring since 1901. This was the first step to answering other questions I had on my mind:
- How poor was the offensive performance of the 2010 Seattle Mariners?
- Are they showing any signs of improvement?
- And how can I use R to tabulate the data to answer these questions?
As I started into this, the first decision was to draw a line in the historical record. I opted to use the eras described in Bill James' "Dividing Baseball History into Eras" article (behind a pay wall – but chances are if you're reading my blog, you already a Bill James subscriber):
- Era 1 (The Pioneer Era), 1871-1892
- Era 2 (The Spitball Era), 1893-1919
- Era 3 (The Landis Era), 1920-1946
- Era 4 (The Baby Boomers Era), 1947-1968
- Era 5 (The Artifical Turf Era), 1969-1992
- Era 6 (The Camden Yards Era), 1993-2012
The second step was to calculate a runs per game (RPG) for each team, by year. This corrects for the longer regular season in the post-expansion period, the strike-shortened seasons, and will give us a common denominator to compare the results so far in 2012.
To do this, I accessed the 2012 edition of the Lahman database. Once I had downloaded and extracted the comma-delimted version of the files, I read the "teams" file into R.
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