Clearly and Simply

Tag: value by area map

  • Cartograms in Microsoft Excel

    How to create Cartograms in Microsoft Excel

    Cartograms in ExcelThe article Cartograms in Tableau described the limitations of Choropleth Maps under certain circumstances and why Cartograms can sometimes be a viable alternative to color coded maps.

    Building upon that, the previous post (Create your own Cartograms in Tableau) provided a Microsoft Excel tool to create the polygons for Cartograms based on your own data. The Excel tool (called Cartogram Data Generator) is based on my VBA implementation of “an algorithm to construct continuous area cartograms” by J. Dougenik, N. Chrisman and D. Niemeyer, published in “Professional Geographer” back in 1985.

    With this VBA algorithm and two other techniques previously published here (Faster Choropleth Maps with Microsoft Excel and Create Excel Freeform Shapes from Polygons), we have all modules available to calculate and plot Cartograms directly in a stand-alone Microsoft Excel workbook.

    Today’s post describes how to create Cartograms in Microsoft Excel and provides two versions of the Cartogram workbook for free download.

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  • Create your own Cartograms in Tableau

    The Cartogram Data Generator: a free Excel Tool to create your own polygon data for plotting Cartograms in Tableau

    Cartogram EUOne of the recent posts showed how Cartograms can be a viable alternative when Choropleth or Filled Maps are stretched to their limits and tell the wrong overall story:

    Cartograms in Tableau

    The article included a Tableau Public dashboard comparing Filled Maps with Cartograms for the results of the US Presidential Elections since 1900.

    Since Tableau does not provide Cartograms as a built-in chart type, the distorted polygons have to be calculated outside of Tableau and then used as a data source to plot the maps using Tableau’s polygon map approach.

    Today’s article is the follow-up post. It provides a free and open Microsoft Excel workbook to create Cartogram data with a few mouse clicks: copy in the data and the original polygon points of all regions and let the tool create a ready-to-use data set to plot Cartograms in Tableau.

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  • Cartograms in Tableau

    Plotting preprocessed polygon data as Cartograms in Tableau: the results of the US Presidential Elections since 1900

    Cartograms of the US Presidential Elections plotted in TableauChoropleth Maps or Filled Maps (as they are called in Tableau) are a great technique for analyzing geographical data, especially for maps with a high level of detail (e.g. US by counties or ZIP codes). They make it very easy to identify geographical hot spots first and then drill down into these regions using other visualization types.

    Having said that, they also have their limitations and disadvantages. Even worse, under certain circumstances Choropleth Maps can be misleading and visualize the data incorrectly.

    A classic example of misleading Choropleth Maps are the well known US Presidential Election Maps. We all have seen them, right? A map of the USA with color coded states: a red fill color if the Republican candidate won the state and a blue fill color if the Democratic candidate won (and in some years other colors for independent candidates).

    Although these maps correctly depict the geographical distribution of “who won where”, they are usually telling the wrong overall story.

    How come?

    Traditionally Republicans very often win some of the larger states with a small population density like Alaska, Montana and Wyoming (and thereby only a small number of electoral votes). As a consequence red often dominates the color coding of the map, even if the Democratic candidate won the entire election.

    Cartograms are a geographical visualization on a map avoiding this problem. Cartograms are distorting the map by resizing its regions according to e.g. the population, the popular votes or the electoral votes, At the same time the Cartogram algorithm tries to retain the topology of the map as far as possible.

    Today’s article presents a dashboard on Tableau Public comparing a Filled Map with a Cartogram for every US Presidential Election since 1900.

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