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Data Visualization Foundations

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Maps

4:02 with Anwar Montasir

So far, the visualizations we’ve covered have mostly taken place on a grid with a labeled x-axis and y-axis. The exception is the pie chart, but even the pie chart has a fixed shape and strict parameters on how it can be presented. However, sometimes the story you’re telling involves geographic data. It might be possible to convey election results using a bar chart, for example, but users will likely find election information more meaningful when results are visualized by city, state, or county. Let’s take a look at some different ways that data visualization and geographic maps intersect.

Vocabulary

  • Choropleth map: a map created by coloring in existing geographic regions based on the relative frequency of a variable.
  • Proportional symbol map: a map in which existing geographic regions include symbols that increase in size based on the absolute frequency of a variable.
  • Geographic heat map: a map demonstrating the frequency of data points while ignoring geographic boundaries.

Further reading

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    So far, the visualizations we've covered have mostly taken 0:01
    place on a grid with a labeled x axis and y axis. 0:05
    The exception is the pie chart, but even the pie chart has a fixed shape and 0:09
    strict parameters on how it can be presented. 0:14
    However, sometimes the story you're telling involves geographic data. 0:18
    It might be possible to convey election results using a bar chart, for 0:23
    example, but users will likely find election information more meaningful 0:28
    when results are visualized by city, state, or county. 0:34
    Let's take a look at some different ways that data visualization and 0:38
    geographic maps intersect. 0:43
    It's important to note that maps themselves are data visualizations, 0:45
    since they help us make sense of the world around us. 0:49
    In fact, the earliest known data visualization is a map of the town 0:53
    of Konya in Turkey created over 8000 years ago. 0:57
    Of course, these days sophisticated apps like Google Maps provide more than 1:01
    just geographic information, offering features like up to date traffic reports, 1:07
    and suggesting alternate routes to reach your destination. 1:13
    When it comes to plotting data points on a geographic map, 1:17
    the most common methods you'll encounter are choropleth maps, 1:21
    proportional symbol maps, and geographic heat maps. 1:26
    Choropleth maps are created by coloring in existing geographic regions 1:29
    such as counties within a state based on the frequency of a variable. 1:35
    For example, a choropleth map could demonstrate unemployment numbers in 1:40
    various counties throughout the state of California. 1:44
    When plotting this data, 1:47
    note that choropleth maps are only effective when showing relative numbers. 1:49
    The first map on the left shows absolute numbers, but 1:54
    it's not surprising that Los Angeles County has the most unemployed people. 1:58
    After all, Los Angeles County has more than 10 million residents, 2:03
    while some counties in Northeastern California have fewer than 10,000. 2:07
    This second map colors in the counties of California based on 2:12
    the unemployment rates per 100 people, which is far more meaningful. 2:16
    Absolute numbers can be shown using a proportional symbol map, 2:21
    sometimes called a bubble map. 2:26
    Proportional symbol maps are still based on geographic regions such as counties, 2:28
    but the frequency of the variable is represented by the size of the symbol. 2:33
    This map of Oklahoma uses large circles to represent counties with at least 2:38
    40,000 people who identify as American Indian or Alaska Native and 2:44
    small circles to represent counties with smaller numbers. 2:49
    Challenges with proportional symbol maps include the difficulty users 2:53
    might have comparing circle sizes. 2:58
    And also that circles tend to overlap when plotting densely populated areas, 3:01
    such as the Northeastern United States. 3:06
    Sometimes however, your geographic data doesn't need to be constrained by region. 3:10
    Geographic heat maps demonstrate the frequency of data points 3:15
    on a map while ignoring geographic boundaries. 3:19
    For example, the collaborative data science platform called Mode 3:23
    offers an interactive geographic heat map showing the locations of 3:28
    Carl's Jr fast food restaurants in the United States. 3:32
    Red spots on the map represent areas with a high volume of 3:36
    Carl's Jr restaurants in close proximity, 3:40
    while cooler colors indicate areas with fewer Carl's Jr restaurants. 3:44
    So that covers a number of basic types of data visualizations. 3:50
    In the final stage of this course, we'll learn a few more rules to guide you as you 3:54
    put your new knowledge into practice. 3:59

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