Anatomy of a Visualisation - Chris McDowall

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We see the results of creative data visualisation exercises all over the web but it is rare that an audience gets to peek inside the design process. Chris will provide a whirlwind tour of a geographic mashup's creation, before turning to the matter of, "So, what does this actually mean?" Expect to see some maps.... lots of maps.

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  • NZ holds a general election roughly every three years. On election day, usually a Saturday in November, polling stations are established up and down the country.
  • It’s extraordinary when you stop to think about it. We make our way to a local polling booth, complete our voting form and collectively decide who will govern the nation.
  • At 7pm the stations close and an army of volunteers and officials begin counting, checking, double-checking and tabulating our votes.
  • …and the nation waits.
  • The following morning, media outlets publish maps like this one; summaries of how the nation voted broken down by electorates. But it is hard to dig inside that data. The patterns are far more nuanced than the patchwork of red and blue polygons suggest.
  • I want to dig inside. I want to know how does my neighbourhood vote.
  • Finer resolution data exists. The names and counts of polling stations are published on the NZ election results website. However, the geographic coordinates are absent and the data proved difficult to geocode.
  • So, a few weeks ago I wrote to the electoral commision and requested the geographic coordinates.
  • Within hours they provided me with the data.
  • It looked like this.
  • And lo, we have a national map of polling stations.
  • I wrote a Python script that creates a single table containing the geographic coordinates of each polling station and the appropriate party votes counts.
  • The maps on the following slides employ three visual variables to display data. The size of the symbol indicates the number of votes. Colour indicates which party received the majority of votes. Orientation indicates the strength of the majority. The further the symbol leans left, the greater the Labour majority. The further right, the greater the National majority.
  • Here are Auckland party vote results mapped at the level of polling stations. Note the hard National stronghold of the North Shore. See how intense the support is through Epsom across to Howick, broken only by Glen Innes & Tamaki. Observe, complex patchwork of mixed support through central/West Auckland.
  • Same symbols for Christchurch …
  • ...and Wellington.
  • Tonight is about mash-ups. Let’s take two datasets that were never intended to be shown together and overlay them.
  • This is the University of Otago’s Index of deprivation. It maps the relative deprivation of different geographic areas based on a set of variables from the national Census. The more red an area is the greater the level of deprivation. The more blue, the less deprived.
  • Let’s just map those areas that fall below the median level of deprivation. Does this pattern look familiar?
  • Now let’s just overlay those polling stations that strongly voted Labour. I’d say this is a pretty good fit.
  • Similarly, let’s map those areas that were above the median level of deprivation.
  • ...and overlay those polling stations that voted National. This analysis is crude and you should treat these maps with a heavy grain of salt, but they suggest a correlation that warrants further examination.
  • Anatomy of a Visualisation - Chris McDowall

    1. 1. anatomy of a visualisation chris mcdowall
    2. 2. Library van polling booth in Vogeltown, 1950 Evening Post staff photographer. Negatives of the Evening Post newspaper collection. Alexander Turnbull Library, Wellington, NZ. Reference 114/145/13-G
    3. 3. Polling station for 2008 New Zealand general election Photograph by Simon Lyall. Wikimedia Commons.
    4. 4. 1957 General Election results board, Wellington Photographer unidentified. Alexander Turnbull Library, Wellington, NZ. Reference 1/2-101460-F
    5. 5. Crowd in Willis Street, Wellington, awaiting results of the 1931 general election Photograph by William Hall Raine. W H Raine collection. Alexander Turnbull Library, Wellington, NZ. Reference 1/1-004500-G
    6. 6. 2008 Electorate results Dramatic, Wikimedia Commons.
    7. 7. How does my neighbourhood vote?
    8. 8. Party vote counts by polling place, Auckland Central http://www.electionresults.govt.nz/electionresults_2008/e9/html/e9_part8.html
    9. 9. To: enquiries Subject: Geo-locations of polling stations Hello, I am writing to inquire whether it would be possible to obtain a copy of the geographic coordinates of polling stations. I am keen to map of the results of the last general election at the level of the individual polling stations. I see that the http://www.electionresults.govt.nz website publishes the addresses of polling stations. Is this information available in a format that can be used in a GIS (e.g. shapefile) so that it can be mapped. Alternatively, a table of the stations and their latitude, longitude would be fantastic. Please let me know if this is possible. All the best, Chris McDowall
    10. 10. Subject: Geo-locations of polling stations Kia ora, Thank you for your enquiry regarding geographic locations of polling places. Attached you will find a tab separated data file. The file contains name, address, location, meshblock and accessibility data for the physical polling places used at the 2008 general election. Geographic locations are given as Eastings and Northings in the recently superseded New Zealand map grid. The file does not contain locations of advance voting facilities or electorate-level “virtual polling places” for advance votes, special votes, polling places where less than 6 votes at were taken or votes allowed for Party Vote Only. We cannot provide vote data for these virtual polling places at any level of detail finer than the whole-electorate level. The data are as used internally at the 2008 general election. This is the best available information, but should not be considered 100% complete or correct. You will note that a few locations and many meshblocks are missing from the data. I hope this satisfies your requirements.
    11. 11. NZ polling station locations Electoral Commission
    12. 12. NZ polling station locations Data source: Electoral Commission
    13. 13. Total number of votes Party with majority of votes Strength of majority ( National votes – Labour Votes ) Total number of votes
    14. 14. 2008 Polling Station Party Vote Auckland Data source: Electoral Commission
    15. 15. 2008 Polling Station Party Vote Christchurch Data source: Electoral Commission
    16. 16. 2008 Polling Station Party Vote Wellington Data source: Electoral Commission
    17. 17. Is there a relationship between voting patterns and socio-economic deprivation?
    18. 18. NZ Deprivation Index 2006 University of Otago School of Medicine & Health Science
    19. 19. NZ Deprivation Index 2006 – Areas below national median deprivation score University of Otago School of Medicine & Health Science
    20. 20. Areas below NZ median deprivation1 and strong Labour party vote stations2 1) University of Otago School of Medicine & Health Science, 2) Electoral Commission
    21. 21. NZ Deprivation Index 2006 – Areas above national median deprivation score University of Otago School of Medicine & Health Science
    22. 22. Areas above NZ median deprivation1 and strong National party vote stations2 1) University of Otago School of Medicine & Health Science, 2) Electoral Commission
    23. 23. have fun chris mcdowall @fogonwater

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