65 lines
1.4 KiB
Python
65 lines
1.4 KiB
Python
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# Use atan2 instead of acos to calc angle; atan2(x,y) of the point we potentially want to add
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import random
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from collections import namedtuple
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import matplotlib.pyplot as plt
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from math import atan2, degrees, tau, pi
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Point = namedtuple('Point', 'x y')
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Vector = namedtuple('Vector', 'x y')
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def gen_point():
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a = random.uniform(1, 5)
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b = random.uniform(1, 5)
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x_i = random.uniform(1, 5)
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p_i = Point(x_i, a * x_i + b)
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return p_i
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def calc_angle(v1: Vector) -> float:
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# x = atan2(v1.y, v1.x)
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theta_deg = atan2(-v1.y, -v1.x) / pi * 180 + 180
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lel = (90 - theta_deg) % 360
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# degrees = (atan2(-v1.y, -v1.x)) + 180
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return lel
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def calc_vector(p1: Point, p2: Point) -> Vector:
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return Vector((p2.x - p1.x), (p2.y - p1.y))
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def display(points, hull):
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x = [point.x for point in points]
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y = [point.y for point in points]
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h_x = [point.x for point in hull]
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h_y = [point.y for point in hull]
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plt.plot(h_x, h_y, 'ro-')
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plt.scatter(x, y)
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plt.show()
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def rapper(points: set):
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min_pt = min(points)
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hull = [min_pt]
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while True:
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hull.append(min(points - {hull[-1]},
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key=lambda p: calc_angle(calc_vector(hull[-1], p))))
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display(points, hull)
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if hull[-1] == min_pt:
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break
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return hull
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points = {gen_point() for _ in range(10)}
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hull = rapper(points)
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