libpysal.cg.PolygonLocator

class libpysal.cg.PolygonLocator(polygons)

An abstract representation of a polygon indexing data structure.

__init__(polygons)

Returns a polygon locator object.

__init__(Polygon list) -> PolygonLocator

Parameters:

polygonsa list of polygons to index

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> pl = PolygonLocator([p1, p2])
>>> isinstance(pl, PolygonLocator)
True

Methods

__init__(polygons)	Returns a polygon locator object.
contains_point(point)	Returns polygons that contain point
inside(query_rectangle)	Returns polygons that are inside query_rectangle
nearest(query_point[, rule])	Returns the nearest polygon indexed to a query point based on various rules.
overlapping(query_rectangle)	Returns list of polygons that overlap query_rectangle
proximity(origin, r[, rule])	Returns the indexed polygons located within some distance of an origin point based on various rules.
region(region_rect)	Returns the indexed polygons located inside a rectangular query region.

contains_point(point)

Returns polygons that contain point

Parameters:

point: point (x,y)

Returns:

list of polygons containing point

Examples

>>> p1 = Polygon([Point((0,0)), Point((6,0)), Point((4,4))])
>>> p2 = Polygon([Point((1,2)), Point((4,0)), Point((4,4))])
>>> p1.contains_point((2,2))
1
>>> p2.contains_point((2,2))
1
>>> pl = PolygonLocator([p1, p2])
>>> len(pl.contains_point((2,2)))
2
>>> p2.contains_point((1,1))
0
>>> p1.contains_point((1,1))
1
>>> len(pl.contains_point((1,1)))
1
>>> p1.centroid
(3.3333333333333335, 1.3333333333333333)
>>> pl.contains_point((1,1))[0].centroid
(3.3333333333333335, 1.3333333333333333)

inside(query_rectangle)

Returns polygons that are inside query_rectangle

Notes

inside means the intersection of the query rectangle and a polygon is not empty and is equal to the area of the polygon

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> p3 = Polygon([Point((7, 1)), Point((8, 7)), Point((9, 1))])
>>> pl = PolygonLocator([p1, p2, p3])
>>> qr = Rectangle(0, 0, 5, 5)
>>> res = pl.inside( qr )
>>> len(res)
1
>>> qr = Rectangle(3, 7, 5, 8)
>>> res = pl.inside( qr )
>>> len(res)
0
>>> qr = Rectangle(10, 10, 12, 12)
>>> res = pl.inside( qr )
>>> len(res)
0
>>> qr = Rectangle(0, 0, 12, 12)
>>> res = pl.inside( qr )
>>> len(res)
3

nearest(query_point, rule='vertex')

Returns the nearest polygon indexed to a query point based on various rules.

nearest(Polygon) -> Polygon

Parameters:

query_pointa point to find the nearest indexed polygon to

rulerepresentative point for polygon in nearest query.

vertex – measures distance between vertices and query_point centroid – measures distance between centroid and query_point edge – measures the distance between edges and query_point

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> pl = PolygonLocator([p1, p2])
>>> try: n = pl.nearest(Point((-1, 1)))
... except NotImplementedError: print("future test: str(min(n.vertices())) == (0.0, 1.0)")
future test: str(min(n.vertices())) == (0.0, 1.0)

overlapping(query_rectangle)

Returns list of polygons that overlap query_rectangle

Notes

overlapping means the intersection of the query rectangle and a polygon is not empty and is no larger than the area of the polygon

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> p3 = Polygon([Point((7, 1)), Point((8, 7)), Point((9, 1))])
>>> pl = PolygonLocator([p1, p2, p3])
>>> qr = Rectangle(0, 0, 5, 5)
>>> res = pl.overlapping( qr )
>>> len(res)
2
>>> qr = Rectangle(3, 7, 5, 8)
>>> res = pl.overlapping( qr )
>>> len(res)
1
>>> qr = Rectangle(10, 10, 12, 12)
>>> res = pl.overlapping( qr )
>>> len(res)
0
>>> qr = Rectangle(0, 0, 12, 12)
>>> res = pl.overlapping( qr )
>>> len(res)
3
>>> qr = Rectangle(8, 3, 9, 4)
>>> p1 = Polygon([Point((2, 1)), Point((2, 3)), Point((4, 3)), Point((4,1))])
>>> p2 = Polygon([Point((7, 1)), Point((7, 5)), Point((10, 5)), Point((10, 1))])
>>> pl = PolygonLocator([p1, p2])
>>> res = pl.overlapping(qr)
>>> len(res)
1

proximity(origin, r, rule='vertex')

Returns the indexed polygons located within some distance of an origin point based on various rules.

proximity(Polygon, number) -> Polygon list

Parameters:

originthe point to find indexed polygons near

rthe maximum distance to find indexed polygon from the origin point

rulerepresentative point for polygon in nearest query.

vertex – measures distance between vertices and query_point centroid – measures distance between centroid and query_point edge – measures the distance between edges and query_point

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> pl = PolygonLocator([p1, p2])
>>> try:
...     len(pl.proximity(Point((0, 0)), 2))
... except NotImplementedError:
...     print("future test: len(pl.proximity(Point((0, 0)), 2)) == 2")
future test: len(pl.proximity(Point((0, 0)), 2)) == 2

region(region_rect)

Returns the indexed polygons located inside a rectangular query region.

region(Rectangle) -> Polygon list

Parameters:

region_rectthe rectangular range to find indexed polygons in

Examples

>>> p1 = Polygon([Point((0, 1)), Point((4, 5)), Point((5, 1))])
>>> p2 = Polygon([Point((3, 9)), Point((6, 7)), Point((1, 1))])
>>> pl = PolygonLocator([p1, p2])
>>> n = pl.region(Rectangle(0, 0, 4, 10))
>>> len(n)
2