Choosing the Right Chart for the Job

“The obvious is that which is never seen until someone expresses it simply.” – Kahlil Gibran

Mekko Graphics offers dozens of chart types from which to choose. But how to do you know which chart is the right one for your data? Choosing the correct chart is completely dependent on your message.   The key is ensuring you are using the correct chart is for you to be clear about what point, or message, you want to convey.

Each of our Mekko Graphics chart types, just as a function of the way it organizes your data, is best equipped to emphasize a different message.  Once you know what your message is, it’s easier to figure out which chart type to use.

The key question is what kind of comparison are you trying to communicate?  Gene Zalazny, author of the well-known book Say it With Charts, an Executive’s Guide to Visual Communication, created a matrix to recommend a chart form by highlighting different types of comparisons (page 27).

 

This matrix is a great tool and forces you to start thinking about what types of comparisons you are trying to make. He describes five categories of comparison: component, item, time series, frequency, and correlation, and then recommends broad chart types based on comparison type.

Let’s say you wish to compare your share of sales versus your competitors’ share for a given year. Here, you are comparing components, so perhaps a Pie chart is best. If you wish to compare many values (items) directly, you might use a Cluster Bar chart.  A Stacked Bar might compare parts of several totals. Not shown in the matrix is the Marimekko, a more unique chart for Mekko Graphics. Use a Marimekko when you want to create a 100% stacked bar, but add an additional dimension, by making the width of the bar as variable instead of fixed.  An example might be to compare sales by competitor by market segment, where market segments are different sizes.  A Line chart generally compares values over time. An XY Scatter chart shows correlation patterns, by comparing two sets of numbers at once, one on the horizontal X axis, one on the vertical Y axis. The data values are scattered across the chart. You have the option of connecting the values with lines, but those lines don't show trends over time. A Bubble chart can be used instead of a Scatter chart if your data has three data series (data series: Related data points that are plotted in a chart. Each data series in a chart has a unique color or pattern and is represented in the chart legend. You can plot one or more data series in a chart. Pie charts have only one data series.), each of which contains a set of values. For example, if you wish to chart number of products, dollar value of sales, and percentage size of market share.

Sometimes one chart type is best for part of your data, but another chart type is best for the rest. You don't have to choose one or the other. Instead, Mekko Graphics offers combination chart types. For example, you may use a Bar Line combination chart to display the differences between projected sales and actual sales.

If the multiple sets of data in a combination chart use vastly different scales, then a secondary axis is often needed. Perhaps you wish to show sales revenue, and also display commissions, calculated on the basis of sales revenue. The value of the commissions is only a small percentage of the value of the sales. You can solve this problem by adding another, secondary, chart axis.  Plotting the values of the commissions on their own axis makes it easy to understand the Line chart.

Zelazny’s tool is very effective as a jumping off point by helping you ask the right questions to clarify the message of your chart.  A successful business chart should help you as well as your audience make sense of what would otherwise be complex numbers and ideas. When designed poorly, charts just confuse. But choosing the right chart and utilizing good chart design will convey your message clearly and effectively.

Comments

[Mike Gil]

This is a really useful post, Betsy, for anyone who cares about presenting information graphically.

Given that pictures really help to tell the story, illustrations of Marimekko charts, (even for those of us familiar with them), combination chart types, and secondary axes in the second half of this post would be SUPER-helpful.

Keep up the great work!

[Mekko Graphics: Betsy Johnson]

Thank you Mike! I appreciate the comment, and in fact, my plan is to expand upon this initial post and highlight specific charts in the matrix for each type of comparison identified by Zelazny. Stay tuned for future posts that get more specific, highlighting example charts displaying these different types of comparisons.