libpysal.cg.LineSegment¶

class libpysal.cg.LineSegment(start_pt, end_pt)[source]¶

Geometric representation of line segment objects.

Examples

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

Create a line segment from two endpoints.

Parameters:¶

start_pt : libpysal.cg.Point¶: The point where the segment begins.
end_pt : libpysal.cg.Point¶: The point where the segment ends.

Methods

`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[source]¶

Returns the minimum bounding box of a LineSegment object.

Returns:¶: self._bounding_box – The bounding box of the line segment.
Return type:¶: libpysal.cg.Rectangle

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()[source]¶

Returns a LineSegment object which has its endpoints swapped.

Returns:¶: line_seg – The LineSegment object which has its endpoints swapped.
Return type:¶: libpysal.cg.LineSegment

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)[source]¶

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

Parameters:¶

other : libpysal.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)[source]¶

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

Parameters:¶

pt : libpysal.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)[source]¶

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

Parameters:¶

pt : libpysal.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[source]¶

Returns the length of a LineSegment object.

Examples

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

property line[source]¶

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

Returns:¶: self._line – The Line object of the line on which the segment lies.
Return type:¶: libpysal.cg.Line

Examples

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

>>> l.b
0.0

property p1[source]¶

Helper method. Do not call directly.

Returns the p1 attribute of the line segment.

Returns:¶: self._p1 – The _p1 attribute.
Return type:¶: libpysal.cg.Point

Examples

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

property p2[source]¶

Helper method. Do not call directly.

Returns the p2 attribute of the line segment.

Returns:¶: self._p2 – The _p2 attribute.
Return type:¶: libpysal.cg.Point

Examples

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

sw_ccw(pt)[source]¶

Sedgewick test for pt being ccw of segment.

Returns:¶: is_ccw – 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.
Return type:¶: bool