Geo neighbors

Find neighboring geographical units within a specified radius.

Using libpysal DistanceBand (fast, requires projected coordinates for accuracy).

build_neighbour_network(neighbours)

Build a NetworkX graph from a neighbour dictionary.

Parameters:

Name	Type	Description	Default
neighbours	dict[str, list[str]]	Mapping of unit ID to list of neighbour unit IDs.	required

Returns:

Type	Description
Graph	nx.Graph: Undirected graph with units as nodes and neighbour relationships as edges.

Example

neighbours = {"A": ["B", "C"], "B": ["A"], "C": ["A"]} G = build_neighbour_network(neighbours) print(G.number_of_nodes(), G.number_of_edges()) 3 2

Source code in may/social_networks/builder_functions/geo/geo_neighbors.py

def build_neighbour_network(neighbours: dict[str, list[str]]) -> "nx.Graph":
    """
    Build a NetworkX graph from a neighbour dictionary.

    Args:
        neighbours (dict[str, list[str]]): Mapping of unit ID to list of neighbour unit IDs.

    Returns:
        nx.Graph: Undirected graph with units as nodes and neighbour relationships as edges.

    Example:
        >>> neighbours = {"A": ["B", "C"], "B": ["A"], "C": ["A"]}
        >>> G = build_neighbour_network(neighbours)
        >>> print(G.number_of_nodes(), G.number_of_edges())
        3 2
    """
    import networkx as nx

    # Build graph
    G = nx.Graph()

    # Add all nodes
    for unit_name in neighbours.keys():
        G.add_node(unit_name)

    # Add edges (undirected, so only add once)
    for unit_name, unit_neighbours in neighbours.items():
        for neighbour_name in unit_neighbours:
            if not G.has_edge(unit_name, neighbour_name):
                G.add_edge(unit_name, neighbour_name)

    logger.info(
        f"Built network: {G.number_of_nodes()} nodes, {G.number_of_edges()} edges"
    )

    return G

find_neighbours(*args, method='libpysal', **kwargs)

Find neighbouring geographical units within a specified radius.

Parameters:

Name	Type	Description	Default
*args		Arguments passed to the underlying neighbour finder method.	()
method	str	Method for finding neighbours. Options: 'libpysal' (fast, uses Euclidean distance), 'balltree' (accurate, uses haversine).	'libpysal'
**kwargs		Keyword arguments passed to the underlying method, typically: - geo_units (list[GeographicalUnit]): Units with coordinates. - radius_km (float): Search radius in kilometers.	{}

Returns:

Type	Description
dict[id, list[id]]	dict[str, list[str]]: Mapping of unit ID to list of neighbour unit IDs.

Example

from may.geography import Geography geo = Geography(data_dir="data/geography") geo.load_from_csv() units = list(geo.get_units_by_level("SGU").values()) neighbours = find_neighbours(units, radius_km=10.0, method='libpysal')

Source code in may/social_networks/builder_functions/geo/geo_neighbors.py

def find_neighbours(*args, method="libpysal", **kwargs) -> dict[id, list[id]]:
    """
    Find neighbouring geographical units within a specified radius.

    Args:
        *args: Arguments passed to the underlying neighbour finder method.
        method (str): Method for finding neighbours. Options: 'libpysal' (fast,
            uses Euclidean distance), 'balltree' (accurate, uses haversine).
        **kwargs: Keyword arguments passed to the underlying method, typically:
            - geo_units (list[GeographicalUnit]): Units with coordinates.
            - radius_km (float): Search radius in kilometers.

    Returns:
        dict[str, list[str]]: Mapping of unit ID to list of neighbour unit IDs.

    Example:
        >>> from may.geography import Geography
        >>> geo = Geography(data_dir="data/geography")
        >>> geo.load_from_csv()
        >>> units = list(geo.get_units_by_level("SGU").values())
        >>> neighbours = find_neighbours(units, radius_km=10.0, method='libpysal')
    """
    find_neighbours_method = neighbour_finders[method]
    if find_neighbours_method is None:
        raise ValueError(f"Unknown method: {method}")
    return find_neighbours_method(*args, **kwargs)

register_neighbour_finder(name)

Decorator to register a neighbour finding method in the neighbour_finders registry.

Parameters:

Name	Type	Description	Default
name	str	Name to register the neighbour finder under.	required

Returns:

Name	Type	Description
Callable		Decorator function that registers the wrapped function.

Example

@register_neighbour_finder("my_method") ... def find_neighbours_my_method(geo_units, radius_km): ... return {} neighbours = neighbour_finders"my_method"

Source code in may/social_networks/builder_functions/geo/geo_neighbors.py

def register_neighbour_finder(name: str):
    """
    Decorator to register a neighbour finding method in the neighbour_finders registry.

    Args:
        name (str): Name to register the neighbour finder under.

    Returns:
        Callable: Decorator function that registers the wrapped function.

    Example:
        >>> @register_neighbour_finder("my_method")
        ... def find_neighbours_my_method(geo_units, radius_km):
        ...     return {}
        >>> neighbours = neighbour_finders["my_method"](units, 10.0)
    """

    def decorator(func: GraphCreator):
        neighbour_finders[name] = func
        return func

    return decorator