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Basic Examples
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To create any polyhedron, first define the symbols used. Then use the polyhedron functions to define the constraints. The following is a simple running example illustrating some different operations and properties that can be performed by LinPy with two squares.
>>> from linpy import *
>>> square1 = Le(0, x) & Le(x, 2) & Le(0, y) & Le(y, 2)
>>> square1
And(Ge(x, 0), Ge(-x + 2, 0), Ge(y, 0), Ge(-y + 2, 0))
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Binary operations and properties examples:
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>>> square2 = Le(1, x) & Le(x, 3) & Le(1, y) & Le(y, 3)
- >>> #test equality
+ >>> #test equality
>>> square1 == square2
False
>>> # compute the union of two polyhedrons
>>> square1 | square2
- Or(And(Ge(x, 0), Ge(-x + 2, 0), Ge(y, 0), Ge(-y + 2, 0)), And(Ge(x - 1, 0), Ge(-x + 3, 0), Ge(y - 1, 0), Ge(-y + 3, 0)))
+ Or(And(Ge(x, 0), Ge(-x + 2, 0), Ge(y, 0), Ge(-y + 2, 0)), \
+ And(Ge(x - 1, 0), Ge(-x + 3, 0), Ge(y - 1, 0), Ge(-y + 3, 0)))
>>> # check if square1 and square2 are disjoint
>>> square1.disjoint(square2)
False
And(Ge(x - 1, 0), Ge(-x + 2, 0), Ge(y - 1, 0), Ge(-y + 2, 0))
>>> # compute the convex union of two polyhedrons
>>> Polyhedron(square1 | sqaure2)
- And(Ge(x, 0), Ge(y, 0), Ge(-y + 3, 0), Ge(-x + 3, 0), Ge(x - y + 2, 0), Ge(-x + y + 2, 0))
-
+ And(Ge(x, 0), Ge(y, 0), Ge(-y + 3, 0), Ge(-x + 3, 0), \
+ Ge(x - y + 2, 0), Ge(-x + y + 2, 0))
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Unary operation and properties examples:
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>>> square1.isempty()
False
>>> square1.symbols()
>>> # project out the variable x
>>> square1.project([x])
And(Ge(-y + 2, 0), Ge(y, 0))
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Plot Examples
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>>> diamond.points()
[Point({x: -1, y: 0}), Point({x: 0, y: -1}), Point({x: 0, y: 0}), \
Point({x: 0, y: 1}), Point({x: 1, y: 0})]
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The user also can pass another plot to the :meth:`plot` method. This can be useful to compare two polyhedrons on the same axis. This example illustrates the union of two squares.
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>>> from linpy import *
>>> import matplotlib.pyplot as plt
>>> from matplotlib import pylab
>>> square2.plot(plot, facecolor='blue', alpha=0.3)
>>> squares = Polyhedron(square1 + square2)
>>> squares.plot(plot, facecolor='blue', alpha=0.3)
- >>> pylab.show()
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+ >>> pylab.show()
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.. figure:: images/union.jpg
- :align: center
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+ :align: center
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