These best practices reflect recommendations shared by a cross-functional team of seasoned Lookers. These insights come from years of experience working with Looker customers from implementation to long-term success. The practices are written to work for most users and situations, but as always use best judgment when implementing.
This Help Center article explains how to choose a visualization type that will be most easily understood by users, based on the kind of information being displayed.
Visualizations are the quickest way of communicating insights found in the data. Choosing the right visualization is a vital component of effectively sharing information across an organization. A few overarching things to consider:
- Think about how other viewers of a visualization will interpret and take action on what they see. Be sure to focus on actionable metrics over vanity metrics.
- Use the simplest visualization possible to communicate a message. Overcomplicated visualizations are difficult to understand quickly, and easy to misinterpret.
- Label axes and measures clearly.
- Use consistent colors (use a built-in color palette or implement a custom color palette to help with this).
Below are some common chart types, along with a few best practices, to consider for each category. For a complete list of visualization options, please check out our Documentation.
Column and Bar Charts
Column and bar charts are great for comparing two or more concrete categorical values. The human brain can quickly compare lengths and then grasp the relationship between the categories presented. Column and bar charts differ mainly in orientation. Bar charts are oriented horizontally, while column charts are oriented vertically.
- Consider using a bar chart over a column chart when dimension axis labels are long.
- Use horizontal labels whenever possible, to ensure they are readable.
- The measure axis should typically start at 0 to avoid misleading viewers (but can be unpinned from 0 in circumstances where the insight being shown is completely lost otherwise, i.e. very small differences or changes across data points).
- Always choose a column chart over a bar chart when comparing values over time.
- Consider choosing a bar chart over a column chart when displaying negative values
Line and Area Charts
Line and area charts are best for displaying continuous data, such as time. Discrete data points will be plotted, but those points are then connected, representing continuity between them. Both line and area charts facilitate trend analysis. Although these charts are similar, they should not be used interchangeably. Line charts are best used for comparing performance among groups or for showing more than one measure. Area charts are best for showing cumulative, part-to-whole relationships.
- Be thoughtful when stacking line charts, as this is easy to misinterpret because there are no cognitive clues to indicate that the line values are cumulative.
- Be thoughtful when using area charts for comparing individual groups, because the colors in the back quickly become obscured by the overlapping colors in front.
- It’s best to start the y-axis at 0, to ensure no misinterpretation of the data. If you need to zoom in on a particular trend, you can always place both versions together on a dashboard to ensure viewers have the full picture.
Stacked charts, such as stacked bar charts or stacked area charts, enable you to add complexity to a visualization, by incorporating an additional dimension or additional measures. However, these can also be difficult to read when not implemented properly.
- Avoid using stacked charts to visualize measures that shouldn’t accumulate, such as averages.
- Avoid plotting too many lines or categories at once (5 or fewer is ideal).
Dual Axis Charts
Use dual axis charts to visualize the relationship between two different measures. This may help to show trends or correlations present between those measures, that otherwise would not be obvious if those measures were plotted separately. These are often used when combining measures on very different number scales, such as total values with percentages.
- It is typically best to place the primary measure on the left-side y-axis, as people tend to look to the left first (similar to how they would read from left to right).
- Consider combining different mark styles (such as a line and a bar) to clearly illustrate each measure.
- Use contrasting colors for each measure, to further clarify which is which.
Pie and Donut Charts
- Pie and donut charts can be used to show how a value or measure is split out across categories. Because segments in these charts should always add up to 100 percent, pie and donut charts provide viewers with a sense of the proportions of the pie that can be attributed to each category. These types of charts can be great for showing the general composition of the data, but they should not be used for comparing individual sections to each other or for representing exact values.
- Include fewer than 5 categories in the pie or donut chart whenever possible.
- Choose visualizations like column and bar charts over pie and donut charts, whenever possible, because differences in angles and circular areas can be difficult for the brain to detect.
For more on choosing the best visualizations for the data you want to display, please check out our eLearning course, Designing Great Dashboards.