Graduated symbology

Drive a feature's color (or size) by a numeric field, using class breaks or a continuous ramp.

intermediate

Graduated symbology binds a feature's color and / or size to the value of a numeric field. Use for parcel acreage, incident count, household income, anything where a numeric magnitude should map visually onto the feature.

Two flavors:

  • Class breaks. Define N break values; each range gets its own fill color (or size). The map renders as a step-graded choropleth.
  • Continuous ramp. A min and max color; every feature's color is interpolated along the ramp by its value.

Inputs

  • A layer on the map.
  • A numeric field (integer, decimal, computed numeric).
  • A classification method (class-breaks mode): - Quantile (equal feature count per class). - Equal interval (equal value range per class). - Natural breaks (Jenks) (groupings that minimize within- class variance). - Manual (pick the break values yourself).
  • A color ramp (one of the built-ins, or a custom min→max pair).
  • Optional size graduation: small radius at low value, large at high, for point layers.

How to set it

  1. In the map builder's layer style panel, pick Graduated.
  2. Pick the field.
  3. Pick Class breaks or Continuous.
  4. For class breaks, choose method and class count. Adjust the break values if needed.
  5. Pick a color ramp.
  6. Save.

When to pick class breaks vs. continuous

  • Class breaks when the audience wants legible categories ("low / medium / high"). Easier to read on a paper legend.
  • Continuous when the magnitude matters and the audience can reference a color bar. Looks smoother; harder to read off the exact value.

Notes

  • Outliers wreck equal-interval. One feature with a value 10x larger than the rest collapses the legend. Quantile or Jenks handles this better.
  • Diverging vs. sequential ramps. Use a sequential ramp (one color darkening) for "more of one thing." Use a diverging ramp (two colors meeting at a midpoint) for "difference from a reference value" (positive vs. negative growth, for example).
  • NULL is excluded. Features with NULL in the chosen field are drawn with the fallback symbol (set in the style panel) or hidden. They're never classed alongside numeric values.