FORTH GO

I’ve updated the cluster analysis based on comments received. Thanks to Ed Harrison, I have included data from the Durham County precincts. And since other commenters explained away the apparent under-voting in some precincts, I recalculated the percentages to be based on the number of people voting in that race instead of the total ballots cast for the precinct. For town council, I approximated 4 votes per person which is necessarily on the high side, but makes the town council percentages comparable to the mayor percentages.

Two cluster of precincts and candidates

I also figured out how to color the clusters by absolute values rather than relative values, which helps to differentiate the candidates. They still fall into two large groups, but now it’s easier to see subgroups. Mayor-council alignments are highly sensitive to the council multiplication factor (4 here), so ignore Kleinschmidt and Czajkowski for candidate clustering.

For the record, low scoring candidates have been eliminated (otherwise they make all precincts look more similar), and absentee and provisional votes have been combined with One Stop precincts.

The precincts present a similar clustering as before, except the under-voters are now distributed into other clusters. The yellow group is fairly neutral. The green group is left leaning. The purple group is left-leaning with a focus on Harrison/Rich/Easthom. The blue group is left-leaning with a focus on Merritt/Kleinschmidt. The red group is right-leaning and includes two of the Durham precincts.

As a bonus, I thought this visual was attractive. It shows a smoothed trend line of the vote percentages (times four for town council candidates) by precinct, where the precincts are ordered by support for Kleinschmidt, the winner of the race for mayor. (Click graph for a larger version.)

The “left-leaning” candidates generally rise with Kleinschmidt while the “right-leaning” candidates (dotted lines) fall. Merritt’s strong showing at Lincoln and Northside is also evident. Unfortunately for him, those precincts had very low turn-out.

Damon Seils provided some great maps of the precinct results from this month’s local elections. I played around with the data, and found the results of a two-cluster analysis to be interesting. The ballots don’t include party affiliation, but candidates fell into two clusters, anyway, and the precincts fit several different profiles in support of those two candidate groups.

Two-way clustering of candidates and precincts

I’ll agree the diagram looks a bit complicated, but if you put in a little work, there’s a few gems to be found. Precincts are listed down the left side, and candidates across the bottom. The square at each precinct-candidate intersection is colored according to the candidate’s relative support at that precinct, red being strong, gray medium and blue weak. That part’s called a cell plot or heat map.

The tree-like parts are dendrograms, which show the results of the hierarchical cluster analyses. Similar items (precincts or candidates) are grouped together in the tree.

For the candidates, along the bottom, there’s a clear pair of clusters, which I’ll call left-leaning and right-leaning candidates. Coincidently, the left-leaning are on the left and the right-leaning are on the right.

The precincts are more interesting, though I have even less knowledge of their actual political orientations. I’ve colored the precincts into five groups. The first (red) and to a greater extent the second (yellow) cluster generally voted in favor of the right-leaning candidates. That is, the left six columns of the heat map are bluish and the right four columns are reddish. The opposite is true for the green and purple clusters; they’re more left-leaning, especially the purple precincts.

What puzzles me is the middle (blue) cluster. Those precincts don’t seem to like anyone. The numbers I used for clustering were percent of ballots cast, and apparently there were more voters in those precincts with incomplete ballots, voting in some but not all races. For instance, the two major mayoral candidates, Kleinschmidt and Czajkowski, only received votes on 28% and 21%, respectively, of the ballots at the Kings Mill precinct.

That leads to looking at votes per ballot for each race by precinct. Here’s a bar chart with the precincts ordered by town council votes per ballot.

Most precincts had near 100% participation in the mayoral race (exactly 100% for Booker Creek and Coker Hills), and most precincts averaged over three (of four available) votes in the town council race. So only the already-identified cluster of three (plus Dogwood Acres to a lesser degree) stand out regarding participation.

I imagine the One Stop (early voting for all precincts) totals reflect a lot of Carrboro voters. What makes the others different? Were people there to vote for a different race, like the school board? Or just voting for a favorite son/daughter candidate?