Equal Area Class Break Generator

Cumulative feature-area weighted class upper boundaries; indivisible features and tied values cannot guarantee equal physical areas.

Description

Generate class upper bounds from cumulative feature-area targets.

Area-weighted map classification groups observations using the physical areas of their features, rather than aiming for equal feature counts. Large indivisible features can prevent classes from having equal areas.

When to use this tool

Generate class upper bounds from cumulative feature-area targets. Use it when the input measurements and conventions below match the operation you need.

Prepare observedValues, actualFeatureAreas, classes, respecting the measurement basis and boundaries below.
Compare the worked example with your intended operation before reusing its result.

How to use the tool and how it works

Enter every field in the input table using the stated units and exact supported selector spelling where applicable.
Run the tool. Correct input errors before interpreting an output.
Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.

Provide aligned observedValues and strictly positive actualFeatureAreas. The tool sorts by value, accumulates area and selects the first value reaching each target totalArea times class number divided by classes. It returns one upper bound per class and the total area; classes must be an integer from 1 through the smaller of 128 and the observation count.^[1]

Input field	Meaning and units	Accepted input
observedValues	Observed values.	List of finite numbers
actualFeatureAreas	Actual feature areas.	List of finite numbers
classes	Classes.	Finite number

Output field	Interpretation
result	Object containing the following named result fields.
result.upperBounds	Upper bounds list, in the ordering described in the calculation.
result.totalArea	Total area; use the stated units and sign convention.

json

{
  "input": {
    "observedValues": [
      1,
      2,
      3
    ],
    "actualFeatureAreas": [
      1,
      1,
      2
    ],
    "classes": 2
  },
  "output": {
    "result": {
      "upperBounds": [
        2,
        3
      ],
      "totalArea": 4
    }
  }
}

Limitations and assumptions

Features are not split and tied values can repeat boundaries. Equal target areas do not guarantee equal realized class areas or determine how a renderer assigns boundary values.
Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.

Alternative or Complementary methods

For a map-layout decision, inspect the rendered map at its intended size as well as its numerical dimensions. For classification or coordinate work, retain the chosen boundary and coordinate conventions with the result. Compare the scope of the nearby tools below before substituting one.

References

Tool behavior and example: Equal Area Class Break Generator — tool.io

Similar or alternative tools

Equal Interval Class Break Generator
Equal attribute interval boundaries; does not equalize feature counts or map areas.
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