libpysal.cg.Polygon¶

class libpysal.cg.Polygon(vertices, holes=None)[source]¶

Geometric representation of polygon objects.

Attributes

verticeslist: Returns the vertices of the polygon in clockwise order.
lenint: Returns the number of vertices in the polygon.
perimeterfloat: Returns the perimeter of the polygon.
bounding_boxRectangle: Returns the bounding box of the polygon.
bboxList: Returns the bounding box of the polygon as a list
areafloat: Returns the area of the polygon.
centroidtuple: Returns the centroid of the polygon

__init__(self, vertices, holes=None)[source]¶

Returns a polygon created from the objects specified.

__init__(Point list or list of Point lists, holes list ) -> Polygon

Parameters

verticeslist – a list of vertices or a list of lists of vertices.
holeslist – a list of sub-polygons to be considered as holes.
is_quad_tree_structure_built: : bool – record if the quad tree structure has been built for this polygon. This quad tree structure could help speed up the contains_point test

Examples

>>> p1 = Polygon([Point((0, 0)), Point((1, 0)), Point((1, 1)), Point((0, 1))])

Methods

`__init__`(self, vertices[, holes])	Returns a polygon created from the objects specified.
`build_quad_tree_structure`(self)	Build the quad tree structure for this polygon.
`contains_point`(self, point)	Test if polygon contains point

Attributes

`area`	Returns the area of the polygon.
`bbox`	Returns the bounding box of the polygon as a list
`bounding_box`	Returns the bounding box of the polygon.
`centroid`	Returns the centroid of the polygon
`holes`	Returns the holes of the polygon in clockwise order.
`len`	Returns the number of vertices in the polygon.
`parts`	Returns the parts of the polygon in clockwise order.
`perimeter`	Returns the perimeter of the polygon.
`vertices`	Returns the vertices of the polygon in clockwise order.

property area¶

Returns the area of the polygon.

area -> number

Examples

>>> p = Polygon([Point((0, 0)), Point((1, 0)), Point((1, 1)), Point((0, 1))])
>>> p.area
1.0
>>> p = Polygon([Point((0, 0)), Point((10, 0)), Point((10, 10)), Point((0, 10))],[Point((2,1)),Point((2,2)),Point((1,2)),Point((1,1))])
>>> p.area
99.0

property bbox¶

Returns the bounding box of the polygon as a list

See also bounding_box

property bounding_box¶

Returns the bounding box of the polygon.

bounding_box -> Rectangle

Examples

>>> p = Polygon([Point((0, 0)), Point((2, 0)), Point((2, 1)), Point((0, 1))])
>>> p.bounding_box.left
0.0
>>> p.bounding_box.lower
0.0
>>> p.bounding_box.right
2.0
>>> p.bounding_box.upper
1.0

build_quad_tree_structure(self)[source]¶: Build the quad tree structure for this polygon. Once the structure is built, speed for testing if a point is inside the ring will be inscreased significantly. :return:

property centroid¶

Returns the centroid of the polygon

centroid -> Point

Notes

The centroid returned by this method is the geometric centroid and respects multipart polygons with holes. Also known as the ‘center of gravity’ or ‘center of mass’.

Examples

>>> p = Polygon([Point((0, 0)), Point((10, 0)), Point((10, 10)), Point((0, 10))], [Point((1, 1)), Point((1, 2)), Point((2, 2)), Point((2, 1))])
>>> p.centroid
(5.0353535353535355, 5.0353535353535355)

contains_point(self, point)[source]¶

Test if polygon contains point

Notes

Points falling exactly on polygon edges may yield unpredictable results

Examples

>>> p = Polygon([Point((0,0)), Point((4,0)), Point((4,5)), Point((2,3)), Point((0,5))])
>>> p.contains_point((3,3))
1
>>> p.contains_point((0,6))
0
>>> p.contains_point((2,2.9))
1
>>> p.contains_point((4,5))
0
>>> p.contains_point((4,0))
0
>>>

Handles holes

>>> p = Polygon([Point((0, 0)), Point((0, 10)), Point((10, 10)), Point((10, 0))], [Point((2, 2)), Point((4, 2)), Point((4, 4)), Point((2, 4))])
>>> p.contains_point((3.0,3.0))
False
>>> p.contains_point((1.0,1.0))
True
>>>

property holes¶

Returns the holes of the polygon in clockwise order.

holes -> Point list

Examples

>>> p = Polygon([Point((0, 0)), Point((10, 0)), Point((10, 10)), Point((0, 10))], [Point((1, 2)), Point((2, 2)), Point((2, 1)), Point((1, 1))])
>>> len(p.holes)
1

property len¶

Returns the number of vertices in the polygon.

len -> int

Examples

>>> p1 = Polygon([Point((0, 0)), Point((0, 1)), Point((1, 1)), Point((1, 0))])
>>> p1.len
4
>>> len(p1)
4

property parts¶

Returns the parts of the polygon in clockwise order.

parts -> Point list

Examples

>>> p = Polygon([[Point((0, 0)), Point((1, 0)), Point((1, 1)), Point((0, 1))], [Point((2,1)),Point((2,2)),Point((1,2)),Point((1,1))]])
>>> len(p.parts)
2

property perimeter¶

Returns the perimeter of the polygon.

perimeter() -> number

Examples

>>> p = Polygon([Point((0, 0)), Point((1, 0)), Point((1, 1)), Point((0, 1))])
>>> p.perimeter
4.0

property vertices¶

Returns the vertices of the polygon in clockwise order.

vertices -> Point list

Examples

>>> p1 = Polygon([Point((0, 0)), Point((0, 1)), Point((1, 1)), Point((1, 0))])
>>> len(p1.vertices)
4