Reference elements are lines, markers, boxes, or bands that enhance your visualizations, that have a continuous X or Y-axis, by adding more information and context within the same visualization.

Reference elements are versatile and can be used for many different use cases. Lines, for example, can show thresholds, averages, or targets. Boxes or bands are excellent for showing ranges or regions of interest, allowing you to determine, for example, whether measurements fall within the desired upper and lower limits. With markers, you can highlight certain points of interest in the data, and by connecting them with lines, you can show trends over time.

To add a reference element to your visualization, you must first add a reference layer. You can add multiple reference elements to one layer, and you can add multiple layers to the same visualization. You can also group layers to structure them and to easily configure the reference elements within them simultaneously.

All reference elements within the same layer are calculated based on a value and, optionally, a secondary value. Lines and markers only require one value, whereas boxes and bands are usually defined by the range between two values.

You can split the reference elements in the same way as the visualization by category, color, or trellising. In this way, you can, for example, calculate and show one line for each trellis panel instead of showing the same line across all panels.