This article explains how to visualize the deviation (difference or variance) between two measures, such as the difference between the product revenue streams over two years, or the difference between actual expenses and target expenses for different cost centers.

The first two sections address deviations within a non-time category. The last two sections are dedicated to time-category.

All figures that represent a deviation should include a + or – sign. They can appear in the value axis, close to the data points in the plot area, and in popovers.

Deviation Only

This section explains how to visualize the deviation (difference) between two measures, and only the deviation. The chart below shows the difference between the actual cost and budgeted cost for multiple cost centers.

Deviation in Percentage

It’s a good idea to consider whether the actual value can be given as a percentage when displaying a deviation. The chart below displays the same information as the chart above, but the deviation is expressed in percentage.

If the order is not important, you can also rank items to make the values easy to compare, as illustrated below.

Deviation and Measures

Sometimes you may want to display two measures and the variance (deviation) between them.

The best way to achieve this is by displaying two charts side-by-side: a bullet chart to display the two measures, and a bar chart to display the deviation. Placing the variance (deviation) in a separate chart makes it easy to compare the variance.

The chart below displays the variance between actual expenses and planned expenses for different cost centers and the deviation between them.

For the same reason mentioned above, you should consider displaying the deviation in percentages as illustrated below:

Time Deviation Only

This section explains how to show the deviation over time between two measures, and only the deviation. If you want to show the measures as well, please proceed to the the next section called ‘Time Deviation and Measures’.

Focus on Value

You can use a column chart when the value of the variance is more important than the trend of the variance.

Focus on Trend

Use a line chart if you want to focus on the trend of the variation, as illustrated below.

Sometimes, it’s better to see the deviation as a percentage. In these circumstances, choose one measure as the reference and express the deviation as a percentage of the reference. The chart below contains the same information as the chart above, but with the variation expressed in percentage. You can now see that the deviation in March and June were very high.

Time Deviation and Measures

If you want to display two measures and the deviation in the same visualization, you can use two charts one above the other. And, if the trend of the measures and the variation is important, or if there are many data points, you can use two line charts as illustrated below.

When the value of the variance is more important than the trend of the variance, you can use a bullet chart and a column chart side by side. The chart below displays actual and target values over time, as well as the deviation for each time period.

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