Vulnerability Zones
===================

Definition
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Vulnerability Zones are geographic areas used for analyzing and visualizing vulnerability levels. They divide the study region into discrete units that can be individually assessed and compared.

Purpose
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Vulnerability zones serve several purposes in VERUS:

1. Provide a spatial framework for vulnerability calculations
2. Enable comparisons between different areas of a city or region
3. Create a standardized grid for visualization and mapping
4. Allow for spatial analysis of vulnerability patterns

Types of Vulnerability Zones
----------------------------

VERUS supports several types of vulnerability zones:

* **Hexagonal Grid**: Regular hexagons of uniform size (most common)
* **Administrative Boundaries**: Official boundaries like neighborhoods or districts
* **Custom Polygons**: User-defined areas of interest

The hexagonal grid is often preferred because:

* Hexagons have equal distance from center to all edges
* They tessellate perfectly, avoiding gaps or overlaps
* Their uniform size allows for fair comparison between areas
* They're not influenced by arbitrary administrative boundaries

Creation
--------

Vulnerability zones can be created using the `HexagonGridGenerator`:

.. code-block:: python

    # Create a hexagonal grid with 250m edge length
    grid_gen = HexagonGridGenerator(region="Porto, Portugal", edge_length=250)
    hex_grid = grid_gen.run()

Attributes
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Each vulnerability zone contains several key attributes:

* **Geometry**: The spatial polygon defining the zone
* **Cluster**: The urban cluster the zone belongs to
* **Vulnerability Level**: The calculated vulnerability value
* **Normalized VL**: Vulnerability scaled between 0-1 for comparison
* **Smoothed VL**: Vulnerability after spatial smoothing

Importance in Analysis
----------------------

Vulnerability zones transform point-based PoTI data into a continuous surface of vulnerability values, making it possible to:

1. Identify high-vulnerability hotspots
2. Compare different regions within a city
3. Track changes in vulnerability over time
4. Provide actionable insights for urban planning and emergency management