A heat map is a visualization of objects as blocks in a grid. The blocks are colored to represent an attribute of the object, such as utilization rate. Using color allows the user to quickly access high level information for each object.
When heat map items become so small that they can no longer be meaningfully distinguished, (differs by screen size/resolution) each section of tiny squares begins to act as a single unit grouped together by color. Hovering over a section displays a tooltip with a summary of the items in the section such as their count and which legend entry they represent.
Clicking on the section takes the user to the content view for that item type, filtered to show the items in the clicked section. Whether a single block or group is selected is determined by the size of individual blocks.
The most common use case for a heat map are:
- Users need to quickly assess the utilization rate of objects in a data set. Colored blocks, indicating utilization percentages, provide “at a glance” status which aids in troubleshooting.
- Users need to scan the status of each object in a data set.
Heat Map Variations
Standard Heat Map
- Each block is a square that represents an object in the a data set.
- All blocks should be the same size. The size of blocks are based on the number of blocks in the heat map.
- Blocks are ordered by the attribute status. The object whose attribute is at the highest percentage will be placed in the top-left corner of the map. The remaining object blocks are presented in a descending order (from top-bottom, left-right) by order of percentage.
- The user should be able to click on a block in the heat map to get more detailed information about the object. Design alternatives will be added in a future version of this pattern.
- Block Fill: (optional): Choose a fill color that best reflects the attribute being represented.
- Colors should be based on the PatternFly color palette
- Colors ranges should be relevant to a particular attribute.
- Status thresholds can be represented by the following colors:
- Critical range: Red (#CC0000)
- Warning range: Orange (#EC7A08)
- Trending to Warning: Yellow (#F9D67A)
- No Issues: Light Primary Blue (#BEE1F4)
Tooltip: Tooltips should include the name of the object as well as a summary of the data represented, for example utilization or object status.
- Legend: It is recommended to include a legend to define the colors on the chart. Multiple heat maps may reference a single legend, provided they share the same attribute values. The legend may be located left aligned and underneath the chart or left aligned and to the right of the chart.
- Interactive Legend (optional): Clicking on a series in the legend should toggle the visibility of the series in the chart. Hovering over a series in the legend will highlight the blocks associated with that attribute.
There are two variations of hover dependent on the block size. These variations include a hover state for a single block and a hover state for a collection of blocks.
If the block size is at least 16 x 16px, hovering over a block will dim ALL blocks other than that single block. The tooltip is specific to the object represented by that block. Recommended maximum block size is 50 x 50px
If the block size is smaller than 16x16, hovering over a block will dim all blocks NOT associated with that specific RANGE. The tooltip is specific to the range itself. Recommended minimum block size is 2x2.