Heatmap Range Calculation and Colour Logic

A heatmap legend connects a numeric value to a visual shade. It usually divides the selected metric's observed values into bands, then assigns each band a colour or intensity. Understanding this relationship helps you read the map accurately and avoid treating a shade as if it represented the same number in every view.

What the legend tells you

The legend identifies the value scale used by the current display. In a performance map, it may span negative values through a neutral area to positive values. In an activity or volatility view, the scale may be one-directional or use different labels. Always read the legend that belongs to the current metric, not one remembered from another market or screenshot.

How ranges can be determined

Depending on the provider and selected metric, a heatmap may use fixed thresholds, automatically selected intervals, or another mapping rule. An automatically scaled view can identify the lowest and highest values in the current selection and divide the span into readable bands. When filters or the visible universe change, the endpoints and boundaries may change as well. The exact algorithm is provider-specific, so do not assume every heatmap uses equal-width intervals.

Why similar shades may represent different values

If two maps use different selections, periods or filters, their scales may not match. A vivid shade in one view might correspond to a smaller absolute move than the same shade in another. The same issue can arise when switching from daily change to annual performance or from a two-sided gain/loss metric to a one-direction activity metric. Compare numeric values and legend labels before comparing colour intensity across separate views.

Using legend bands as a filter

Some heatmaps let you click a legend segment to hide the tiles within that range. This can be useful when you want to focus on the strongest positive or negative readings, but it also removes context. If you hide the middle bands, the remaining map may make extremes look more common than they are. Restore the full range when you need to assess the overall distribution.

How to interpret the scale responsibly

1. Confirm the metric and measurement period.
2. Read the minimum, maximum and labels on the legend.
3. Check whether the scale is fixed or appears to adapt to the current selection.
4. Inspect exact values for tiles that matter to your analysis.
5. Re-check the scale after changing filters, grouping or the displayed universe.

Keep size and colour distinct

Tile size and tile colour can describe different variables. A large tile might represent a high market value while its colour shows a modest daily decline. A small tile may have a strong percentage move without having much weight in the selected universe. Interpret each visual channel separately, then combine them only after checking what each one represents.

Range behaviour depends on the data provider and configuration. This guide is for education, not a trading recommendation.