libpysal.cg.LineSegment

class libpysal.cg.LineSegment(start_pt, end_pt)

Geometric representation of line segment objects.

Parameters:

start_ptlibpysal.cg.Point

The point where the segment begins.

end_ptlibpysal.cg.Point

The point where the segment ends.

Attributes:

p1libpysal.cg.Point

HELPER METHOD. DO NOT CALL.

p2Point

HELPER METHOD. DO NOT CALL.

bounding_boxlibpysal.cg.Rectangle

Returns the minimum bounding box of a LineSegment object.

lenfloat

Returns the length of a LineSegment object.

linelibpysal.cg.Line

Returns a Line object of the line on which the segment lies.

Examples

>>> ls = LineSegment(Point((1, 2)), Point((5, 6)))

__init__(start_pt, end_pt)

Methods

__init__(start_pt, end_pt)
get_swap()	Returns a LineSegment object which has its endpoints swapped.
intersect(other)	Test whether segment intersects with other segment (True) or not (False).
is_ccw(pt)	Returns whether a point is counterclockwise of the segment (True) or not (False).
is_cw(pt)	Returns whether a point is clockwise of the segment (True) or not (False).
sw_ccw(pt)	Sedgewick test for pt being ccw of segment.

Attributes

bounding_box	Returns the minimum bounding box of a LineSegment object.
len	Returns the length of a LineSegment object.
line	Returns a Line object of the line on which the segment lies.
p1	**HELPER METHOD.
p2	**HELPER METHOD.

property bounding_box

Returns the minimum bounding box of a LineSegment object.

Returns:

self._bounding_boxlibpysal.cg.Rectangle

The bounding box of the line segment.

Examples

>>> ls = LineSegment(Point((1, 2)), Point((5, 6)))
>>> ls.bounding_box.left
1.0

>>> ls.bounding_box.lower
2.0

>>> ls.bounding_box.right
5.0

>>> ls.bounding_box.upper
6.0

get_swap()

Returns a LineSegment object which has its endpoints swapped.

Returns:

line_seglibpysal.cg.LineSegment

The LineSegment object which has its endpoints swapped.

Examples

>>> ls = LineSegment(Point((1, 2)), Point((5, 6)))
>>> swap = ls.get_swap()
>>> swap.p1[0]
5.0

>>> swap.p1[1]
6.0

>>> swap.p2[0]
1.0

>>> swap.p2[1]
2.0

intersect(other) → bool

Test whether segment intersects with other segment (True) or not (False). Handles endpoints of segments being on other segment.

Parameters:

otherlibpysal.cg.LineSegment

Another line segment to check against.

Examples

>>> ls = LineSegment(Point((5, 0)), Point((10, 0)))
>>> ls1 = LineSegment(Point((5, 0)), Point((10, 1)))
>>> ls.intersect(ls1)
True

>>> ls2 = LineSegment(Point((5, 1)), Point((10, 1)))
>>> ls.intersect(ls2)
False

>>> ls2 = LineSegment(Point((7, -1)), Point((7, 2)))
>>> ls.intersect(ls2)
True

is_ccw(pt) → bool

Returns whether a point is counterclockwise of the segment (True) or not (False). Exclusive.

Parameters:

ptlibpysal.cg.Point

A point lying ccw or cw of a segment.

Examples

>>> ls = LineSegment(Point((0, 0)), Point((5, 0)))
>>> ls.is_ccw(Point((2, 2)))
True

>>> ls.is_ccw(Point((2, -2)))
False

is_cw(pt) → bool

Returns whether a point is clockwise of the segment (True) or not (False). Exclusive.

Parameters:

ptlibpysal.cg.Point

A point lying ccw or cw of a segment.

Examples

>>> ls = LineSegment(Point((0, 0)), Point((5, 0)))
>>> ls.is_cw(Point((2, 2)))
False

>>> ls.is_cw(Point((2, -2)))
True

property len: float

Returns the length of a LineSegment object.

Examples

>>> ls = LineSegment(Point((2, 2)), Point((5, 2)))
>>> ls.len
3.0

property line

Returns a Line object of the line on which the segment lies.

Returns:

self._linelibpysal.cg.Line

The Line object of the line on which the segment lies.

Examples

>>> ls = LineSegment(Point((2, 2)), Point((3, 3)))
>>> l = ls.line
>>> l.m
1.0

>>> l.b
0.0

property p1

HELPER METHOD. DO NOT CALL. Returns the p1 attribute of the line segment.

Returns:

self._p1libpysal.cg.Point

The _p1 attribute.

Examples

>>> ls = LineSegment(Point((1, 2)), Point((5, 6)))
>>> r = ls._get_p1()
>>> r == Point((1, 2))
True

property p2

HELPER METHOD. DO NOT CALL. Returns the p2 attribute of the line segment.

Returns:

self._p2libpysal.cg.Point

The _p2 attribute.

Examples

>>> ls = LineSegment(Point((1, 2)), Point((5, 6)))
>>> r = ls._get_p2()
>>> r == Point((5, 6))
True

sw_ccw(pt)

Sedgewick test for pt being ccw of segment.

Returns:

is_ccwbool

1 if turn from self.p1 to self.p2 to pt is ccw. -1 if turn from self.p1 to self.p2 to pt is cw. -1 if the points are collinear and self.p1 is in the middle. 1 if the points are collinear and self.p2 is in the middle. 0 if the points are collinear and pt is in the middle.