Choosing the right chart type

Charting tools typical offer a number of different types of charts. You may see bar or columns charts, pie charts and Marimekkos. So which chart type would I use to display certain data?

As usual the answer is: it depends. In this case on the message that you would like the slide to tell. Imagine having sales data at hand. You might want to display how the sales revenue developed over time and is projected to grow. It may also be meaningful to analyze the distribution between multiple regions or division. Or you might want to know how the sales volume of multiple products relates to their profitability.

The outcome of your analyses usually falls in a certain category. For a certain category some chart types may be better suited than others. In this blog post and the next we are going to describe the categories comparison, composition, relationship/correlation and frequency/ranking.

Comparison, often a development over time

To see how numbers develop over time typically column and line charts are most powerful. You may add visual elements to highlight or summarize overall growth rates. Tabular data can be used to indicate growth rates for multiple lines or segments in stacked columns.

Stacked bar chart sample

Stacked bar chart sample: US food consumption

For a comparison of multiple items along several criteria spider charts or line charts may be helpful. Use a rotated line chart with lines running top down to visualize a tabular comparison of multiple items.

Line chart sample

Line chart template comparing items on multiple criteria

Composition, sometimes comparing between instances

Composite numbers may tell you how sales are distributed between several divisions. The simplest way to display a 100% composition is to use a pie chart. A single 100% stacked column carries the same information and provides a natural way to add the total number that equals 100%. Showing multiple columns adds a second dimension that allows to compare compositions over time or between several entities. If many periods are displayed it may make sense to use an area chart instead of many stacked columns.

A special chart explaining a composite value is a waterfall chart. Unlike the aforementioned chart types it is capable of showing positive as well as negative values incurring into a composite number. A waterfall chart is especially powerful to display how an input value (e.g. last year’s sales) transforms into a new value (current sales plan) taking into account multiple influencing values (delisted products, new products, additional sales channel).

For breaking down a number into two dimensions a Marimekko can be a good choice. Think about sales figures split across geographies and by product line within each geography.

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