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Adding size to scatter visuals

In Scatter visuals, you can control the size of the individual bubbles to show variation of a measure more clearly.

The World Life Expectancy dataset has several other dimensions and measurements that you can use to enrich the scatter visual. Consider how using the Size shelf, which controls the size of the individual bubbles, changes our immediate understanding of the dataset and represents the relative population size of each country more clearly.

The starting point of the following example is the 'World Population - Scatter' visual developed in Creating basic scatter visuals.

  1. Click Clone to create a new visual that has the same properties as the original.
  2. Under Measures, select population and drag it to the Size shelf.
  3. On the sum(population) field, click the (right arrow) icon to open the FIELD PROPERTIES menu.
  4. Expand Aggregates and select Average.
  5. Click REFRESH VISUAL.
    The Scatter visual appears with its own visible population size 'outliers': China, India, and the United States.
  6. Optional: It is important to realize that the relative size of the bubbles is not linearly proportional to their values.

    At the lower range of population levels, the visual shows the same size marks for countries with very different average populations, such as Tokelau, where avg(population)=1.23K, Greenland, with avg(population)=34.5K, Luxembourg, with avg(population)=318K, and Kuwait, with avg(population)=751K. This is because by default, the size of marks ranges from 10 to 50 pixels. Divided equally across the range of values, this squeezes too many disparate measurements on the lower end to use the same mark size 'bucket'.

    Figure 1. World Population Figures with Mark Size Range of 10 - 50 Pixels

    It is easy to somewhat alleviate this problem by changing the range of sizes of the bubbles, as described in Changing the mark size range. This graph shows the size range of 1-50.

    Figure 2. World Population Figures with Mark Size Range of 1 - 50 Pixels

    Incidentally, and obviously, the increased size range generates a more realistic representation of relative population size.

  7. Click the pencil/edit icon next to the title of the visualization to enter a name for the visual.

    In this example, the title is changed to 'World Population - Scatter with Size'. You can also add a brief description of the visual as a subtitle below the title of the visualization.

  8. At the top left corner of the Dashboard Designer, click SAVE.

While you can see the average data for individual countries more clearly, these measurements do not help you to see the changes that occurred over the entire time domain of the dataset.

As a next step, look at how you can add the concept of time back into the visual by animating the scatter plot, as described in Adding transition animation to scatters.