Maps

Graduated-symbol map

Classifies numeric values and assigns a fixed symbol size to each class.

Map
Geography
Comparison

What it answers

Which magnitude class does each location belong to?

Shape: Symbols in discrete size classes
What it shows: Class-based geographic contrasts.

Example

The question

Which towns fall into each sales band?

Store sales by town in three bands (graduated symbols)

Three symbol sizes for three sales bands (under 10, 10 to 20, over 20 million euros). two towns over 20 (30 and 22), two from 10 to 20 (18 and 12), three under 10.

Illustrative data. It belongs to no company.

When to use it

Use it when

Maps where a few value classes aid reading.

Avoid it when

When exact continuous differences are important.

How to read it

Read discrete size classes and their thresholds.

Note

State class thresholds. Different from continuous proportional sizing.

The data you need

Layout: Long table
Fields: LocationID: text; Longitude,Latitude: numbers; Value: nonnegative number
One row is: One point location and its value or weight. What is the grain?
Rules: State CRS. For WGS84, longitude is [-180,180] and latitude [-90,90]. Validate coordinate order.
Optional: For unweighted density, each point may have weight 1. Project coordinates appropriately for distance calculations.
Preparation: Validate the input grain and missing values. State CRS. For WGS84, longitude is [-180,180] and latitude [-90,90]. Validate coordinate order.
Units: Symbol size represents a declared value class; it is not a continuously proportional value.

A long table: one row per observation, few columns. New data adds rows.

Worked example

Classes 0-20,21-40,41-60 placeA30 in medium and B45 in large. Values 41 and 60 share a symbol size.

LocationID	Longitude	Latitude	Value
A	18.07	59.33	30
B	11.97	57.71	45

All charts in the library