Axes and labels
Axes and labels provide critical context for the information within a chart. Use simple, easy-to-understand descriptors and metrics to label your chart and axes.
Always start numerical axes at zero for part-to-whole and comparisons charts. For bar and area charts, a truncated Y-axis can distort the perceived scale of a chart, making a small difference appear more significant than it is.
It’s acceptable to start line charts and scatter plots at a value higher than zero. These types of visualizations are less sensitive to distortion because they communicate trends rather than difference in size or quantity. In these cases, cropping the Y-axis helps users better identify the direction of change.
Use the designated texture to denote the range or period when data is not available. Always label both start and end points where data is not available.
Sometimes it’s useful to skip part of the axis to bring data on the extreme ends into view without distortion. When axes contain a break, use a sinusoidal line to replace the straight axis line.
On the X-axis, the break may be fluid with graph area size, with a minimum width of 16px. On the Y-axis, we recommend fixing the distance break at 16px.
If data is available during an axis break, restyle line segments to use 0.5px stroke and hide circles representing data points.
If data isn’t available between break points, denote the data gap with a texture.
If any form of axis compression is required, use the provided axis break styling to visually denote the compression.
In time series, X-axis labels reflect the time increment in the data. When possible, use localized date and time format, or user preference. Otherwise, the chart defaults to the format presented below.
Whenever data cross into a new time cycle, such as a new day, month, or year, semibold the label to emphasize the transition.