by    in interest graph, Market Research, Pop Culture

Hierarchical Clustering of a Ranker list of Beers

This is a guest post by Markus Pudenz.

Ranker is currently exploring ways to visualize the millions of votes collected on various topics each month.  I’ve recently begun using hierarchical cluster analysis to produce taxonomies (also known as dendograms), and applied these techniques to Ranker’s Best Beers from Around the World. A dendrogram allows one to visualize the relationships on voting patterns (scroll down to see what a dendrogram looks like). What hierarchical clustering does is break down the list into related groups based on voting patterns of the users, grouping like items with items that were voted similarly by the same users. The algorithm is agglomerative, meaning it is starts with individual items and combines them iteratively until one large cluster (all of the beers in the list)  remains.

Every beer in our dendrogram is related to another at some level, whether in the original cluster or further down the dendrogram. See the height axis on the left side? The lower the cluster is on the axis, the closer the relationship the beers will have. For example, the cluster containing Guinness and Guinness Original is the lowest in this dendrogram indicating these to beers have the closest relationship based on the voting patterns. Regarding our list, voters have the option to Vote Up or Vote Down any beer they want. Let’s start at the top of the dendrogram and work our way down.

Hierarchical Clustering of Beer Preferences

Looking at the first split of the clusters, one can observe the cluster on the right contains beers that would generally be considered well-known including Guinness, Sam Adams, Heineken and Corona. In fact, the cluster on the right includes seven of the top ten beers from the list. The fact that most of our popular beers are in this right cluster indicates that there is a strong order effect with voters more likely to select beers that are more popular when ranking their favorite beers. For example, if someone selects a beer that is in the top ten, then another beer they select is also more likely to be in the top ten. As we examine the right cluster further, the first split divides the cluster into two smaller clusters. In the left cluster, we can clearly see, unsurprisingly, that a drinker who likes Guinness is more likely to vote for another variety of Guinness. This left cluster is comprised almost entirely of Guinness varieties with the exception of Murphy’s Irish Stout. The right cluster lists a larger variety of beer makers including Sam Adams, Stella Artois and Pyramid. In addition, none of the beers in this right cluster are stouts as with the left cluster. The only brewer in this right cluster with multiple varieties is Sam Adams with Boston Lager and Octoberfest meaning drinkers in this cluster were not as brand loyal as in the left cluster. Drinkers in this cluster were more likely to select a beer variety from a different brewer. When reviewing this cluster from the first split in the dendrogram, there is clearly a defined split between those drinkers who prefer a heavier beer (stout) as opposed to those who prefer lighter beers like lagers, pilseners, pale ales or hefeweizen.

Conversely, for beers in the left cluster, drinkers are more likely to vote for other beers that are not as popular with only three of the top ten beers in this cluster. In addition, because of the larger size, the range of beer styles and brewers for this cluster is more varied as opposed to those in the right cluster. The left cluster splits into three smaller clusters before splitting further. One cluster that is clearly distinct is the second of these clusters. This cluster is comprised almost entirely of Belgian style beers with the only exception being Pliny the Elder, an IPA. La Fin du Monde is a Belgian style tripel from Quebec with the remaining brewers from Belgium. One split within this cluster is comprised entirely of beer varieties from Chimay indicating a strong relationship; voters who select Chimay are more likely to also select a different style from Chimay when ranking their favorites.  Our remaining clusters have a little more variety. Our first cluster, the smallest of the three, has a strong representation from California with varieties from Stone, Sierra Nevada and Anchor Steam taking four out of six nodes in the cluster. Stone IPA and Stone Arrogant Bastard Ale have the strongest relationship in this cluster. Our third cluster, the largest of the three, has even more variety than the first. We see a strong relationship especially with Hoegaarden and Leffe.

I was also curious as to whether the beers in the top ten were associated with larger or smaller breweries. As the following list shows,  there is an even split between the larger conglomerates like AB InBev, Diageo, Miller Coors and independent breweries like New Belgium and Sierra Nevada.

  1. Guinness (Diageo)
  2. Newcastle (Heineken)
  3. Sam Adams Boston Lager (Boston Beer Company)
  4. Stella Artois (AB InBev)
  5. Fat Tire (New Belgium Brewing Company)
  6. Sierra Nevada Pale Ale (Sierra Nevada Brewing Company)
  7. Blue Moon (Miller Coors)
  8. Stone IPA (Stone Brewing Company)
  9. Guinness Original (Diageo)
  10. Hoegaarden Witbier (AB InBev)

Markus Pudenz