Bar and Bar-Line Combo Charts
Best Practices
Overview
The primary use of a bar chart is to show comparisons between time periods or categories. One axis shows items to compare while the other displays the value being measured; the longer the bar the greater its value. The primary goal of a bar chart is to showcase the relationship between the two axes. A grouped bar chart visualization is displayed if the data set has multiple data series within it.
The bar-line combo chart type allows you to show one or more data series as lines. You can use this type for mean values, median values, etc. (See example bar-line combo.)
Note that with WCMS Release 4.9.13, you can now create horizontal bar charts. A horizontal orientation helps when data labels for categorical charts are long. It can also help with page layout, particularly when there are many data series to chart. (See example horizontal chart.)
Chart is an interactive content type in the WCMS. Go to examples at the bottom of this page to try out “live” charts.
- Go to ExamplesSee examples on this page that illustrate key options.
- Building in the WCMSSee key tips and guidelines for working with bar charts in the WCMS.
- TP4 UX Best Practices [PPT - 14 MB]For general guidance on colors, layouts, and overall presentation, see this overview of TP4 best practices.
Interacting with the labels in the legend will highlight or isolate the selected data series. Each data series can be toggled on and off individually, allowing users to view a wide variety of combinations.
Sorting: Selecting the top row of a column sorts the entire table by the content within the selected column. Selecting the same column multiple times rotates the sorting feature between three states: Descending, Ascending and Off. Only a single column can be sorted at one time.
Source: When referencing information from outside of the current page, you should provide a source link. Source links should be short and descriptive; they should not be the full URL. Source links are always displayed directly above the table.
Usage
Bar charts are used to easily compare data among categories and between groups at a glance. They reveal patterns, trends, relationships and exceptions in data values that are not readily apparent from a table of values.
Use:
- When comparing categories
- When showing big changes in data
Don’t Use:
- When showing small incremental changes
Other Guidance
- Chart Title: Good titles are invaluable. Your chart title should be long enough so that your audience can make sense of the chart. A glance at the title should clearly convey what the chart contains. A good title requires a balance between a short title and one with enough descriptive information to describe the chart clearly.
- Visual Clutter: Consider the mental burden you are placing on your users. For example, if your chart has a lot of data series, consider using multiple charts. Consult with your UX specialist when in doubt.
- Grid Lines: In most cases, both horizontal and vertical grid lines should be hidden to reduce chart clutter. Approximate values can be perceived without grid lines. When the difference in data values is close, horizontal grid lines can be shown to better support data value comparison.
- Data Source: The data source makes your graphic more reputable. It also allows those who are interested to dig deeper.
- Outliers in Series Bar Data: If the data set includes one or more extreme outliers, the visualization can be difficult to process. If the variation can be seen only on a single bar and the rest are flat, do one of the following: Modify the data set to remove / adjust the outlier issue, split the chart into multiple charts, or select a different chart type.
- Confidence Intervals: Confidence intervals give an indication of the certainty of the dataset. You can configure the chart to show confidence intervals in the configuration tab. See chart example.
Chart Color Palettes
Epi Curve Style Bar Chart
An epidemic curve, or “epi curve,” is a variation of a standard time-based vertical bar chart. It is a visual display of the onset of illness among cases associated with an outbreak. See example data file [XLS – 381 B]
Horizontal Bar Chart
This horizontal bar chart helps allow room for longer data names and provides new layout options. See example data file [XLS – 195 B]
Lollipop Style Bar Chart
This variation of a standard horizontal bar chart creates visual interest and differentiates it from other bar charts. All while retaining the extra space for longer data names. Currently only one data source may displayed per chart. Also, two of the current colors are supported when “Two-Tone” is selected in the visual tab. See example data file [XLS – 195 B]
Standard Time-Based Bar Chart (Vertical)
Note how selecting a data series in the legend isolates the series (whereas in the next example the series is highlighted when selected). See example data file [XLS – 250 B]. Note that you do not have to chart all the data series in the source file. This source file contains 6 data series, but in the Data Series section of the Chart Configuration tab, the developer has selected only 3 series for the chart.
Standard Categorical (Non-Time-Based) Bar Chart
With WCMS release 4.8.2, the bar chart now supports non-time-based data, as illustrated below. See example data file [XLS – 159 B].
Combo Bar-Line Chart
To create a chart like the one below, select Bar as the visualization type. Then in the General section of the Configuration tab, select “Combo” as the chart type. In the Data Series section of the configuration tab, you’ll select which data you want to show as a line or a bar. See example data file [XLS – 318 B]. (Note that you can allow your users to download the table data in CSV format, as illustrated with this chart.)
Stacked Bar Chart
To create a chart like the one below, select “Bar ” as the visualization type and then select the “stacked” chart subtype under the general section of the configure tab. Stacked bars can work well to show percentages when every bar totals 100. See example data file [JSON – 382 B]
Bar with CIs in Visualization
If you have high and low CI columns in your source data, you can easily display them in the visualization area. In the data series section of the configuration tab, select the high and low data sets using the drop down selectors. See example data file [XLS – 113 B].