Recently I'd been noticing some traffic to the site from the Big Footy website where the Forum members had been discussing the relative strengths of Bulldogs teams across VFL/AFL history. That, coupled with my continuing desire to become more proficient in the ggplot2 R package of Hadley Wickham, dragged me out of my off-season blog malaise to perform the analyses underpinning this current posting.

First up I wanted to summarise every team's season-by-season history in a single chart that facilitated comparisons both across time for a single team and across teams for a single point in time. Hence, the chart that follows, which depicts each team's end of season MARS Rating (these Ratings created assuming, inter alia, that the home team in any Final is the team with the higher MARS Rating).

(Please note that this and all other charts in this blog can be clicked to access a larger version.)

As is customary, I'll point out the things that strike me most about this chart, leaving a more detailed and nuanced review to the interested reader: 

• The Bulldogs are perhaps most notable for the fact that they've never had an extended period of exceptionally high end-of-season Ratings. The period from the mid 1930s to about the mid 1950s seems to have been the nearest thing to a Golden Age for the club.
• Sydney have been impressively strong from about the mid 1990s to the current day.
• St Kilda's only periods of exceptionalism have been from the early 1960s to the late 1970s, and from about 2000 to the current time.
• Richmond have been in an extended period of mediocrity from the early 1980s to the present.
• Melbourne have been largely unexceptional from about the mid 1960s to the present day.
• The Roos have had only two eras of relative dominance - in the 1970s and late 1990s - and have not done much besides.
• Hawthorn fielded generally above-average teams from the mid 60s to about the mid 90s, and have only recently re-attained such Ratings.
• Geelong have had a number of mostly brief periods of high Ratings, the most recent period approaching the longest they've enjoyed.
• Essendon have been largely unimpressive since their dominance around the turn of the latest century.
• Collingwood have been amazingly consistent throughout their history and have returned to their traditional above-average end-of-season Ratings over about the last decade.
• Carlton have also enjoyed a remarkable history, though the last decade has seen them atypically uncompetitive.
• Adelaide have avoided especially low end-of-season Ratings throughout their entire history. 

This same data can be viewed in a slightly different way by means of a series of line charts (vaguely reminiscent of killer pythons), one for each team.

What's a little unusual about this chart is that each team's Rating across time is encoded in two ways simultaneously: by vertical height above the y-axis and by colour. I find that this format helps call out extended periods of dominance and inferiority for a particular team of interest, and then lends itself to a more detailed analysis of these periods.

I'll finish today with a chart that records each team's Ratings Change per Game for every season. (We use a per game metric here to compensate those teams playing in significantly shorter seasons.) This chart focusses on teams' increases and decreases in ability relative to their assessed ability at the start of each season, and is divorced to some extent from whether those increments or decrements ultimately led to exceptionally high or exceptionally low Ratings.

Periods of green are those periods where a team has enjoyed intra-season Ratings increases in most years, whereas periods of red represent times where the opposite has been the case.

A few things that stand out for me in this chart are: 

• Carlton's, Collingwood's and Essendon's each having endured only a few periods of frequent Rating decline. (Carlton's early 2000s performance is most noticeable in this context.)
• Fitzroy's struggles from about 1960 to their exit from the competition in the late 1990s 
• Geelong's impressive record over the past decade or so, in which they've managed to generally finish with an end-of-season Rating higher than their start-of-season Rating despite, in many years, starting with an above-average Rating
• Hawthorn's struggles from their inception until about 1970 after which they enjoyed about 20 years of intra-season Rating increases
• The Roos' struggles from their inception until about the mid 1970s after which they enjoyed a period of general improvement without ever turning in any single remarkable season
• The streakiness of the performance of Melbourne and their general history of intra-season Rating declines since about the mid 1960s
• The similar streakiness of the performance of Richmond and their general history of intra-season Rating declines since the early 1980s
• The absence of regular, extended periods of Ratings enrichment for the Saints. The seasons spanning the mid 50s to about the early 70s represent the only period where their teams enjoyed regular, if mostly modest, intra-season increases
• Sydney's very extended period of predominantly declining intra-season Ratings commencing in the late 1940s and extending all the way through to the mid 1990s, followed by an extended period of Ratings increases which persists to the current day
• Absence in the Bulldogs' history of any period of substantial and regular Ratings increases, though the period from the early 1980s through to the first few seasons of the current century did include a preponderance of, at least, modest intra-season gains
• West Coast's general history of intra-seasonal Ratings increases 

Evidence for the efficacy of assessing team performances on a per-game basis - which is largely designed to compensate teams from the earlier parts of VFL/AFL history when seasons were typically short - comes I'd suggest from the fact that tall green and tall red bars seem to appear with similar regularity throughout all periods of VFL/AFL history.