计算和显示 ConvexHull

Question

我正在尝试计算并显示 python 中一些随机点的凸包。

这是我当前的代码：

import numpy as np
import random
import matplotlib.pyplot as plt
import cv2

points = np.random.rand(25,2)   

hull = ConvexHull(points)

plt.plot(points[:,0], points[:,1], 'o',color='c')

for simplex in hull.simplices:
    plt.plot(points[simplex, 0], points[simplex, 1], 'r')

plt.plot(points[hull.vertices,0], points[hull.vertices,1], 'r', lw=-1)
plt.plot(points[hull.vertices[0],0], points[hull.vertices[0],1], 'r-')
plt.show()

我的问题：

• 如何在 0 到 9 之间更改 X、Y 标签和点数限制？例如 (0,1,2,3,4,5,6,7,8,9)
• 如何用圆圈标记凸包上的点？ As in example

Answer 1

将np.rand() 替换为randint(0, 10) 将生成从0,1,... 到9 的整数坐标。

使用“。”作为标记将导致给定点的标记更小。

使用 'o' 作为标记，设置 markeredgecolor 并将主颜色设置为 'none' 将产生一个圆形标记，可用于船体上的点。标记的大小可以通过markersize=调整。

fig, axes = plt.subplots(ncols=..., nrows=...) 是创建多个子图的便捷方式。

下面是一些最小示例的代码：

from scipy.spatial import ConvexHull
import matplotlib.pyplot as plt
import numpy as np

points = np.random.randint(0, 10, size=(15, 2))  # Random points in 2-D

hull = ConvexHull(points)

fig, (ax1, ax2) = plt.subplots(ncols=2, figsize=(10, 3))

for ax in (ax1, ax2):
    ax.plot(points[:, 0], points[:, 1], '.', color='k')
    if ax == ax1:
        ax.set_title('Given points')
    else:
        ax.set_title('Convex hull')
        for simplex in hull.simplices:
            ax.plot(points[simplex, 0], points[simplex, 1], 'c')
        ax.plot(points[hull.vertices, 0], points[hull.vertices, 1], 'o', mec='r', color='none', lw=1, markersize=10)
    ax.set_xticks(range(10))
    ax.set_yticks(range(10))
plt.show()

PS：要在单独的窗口中显示绘图：

from scipy.spatial import ConvexHull
import matplotlib.pyplot as plt
import numpy as np

points = np.random.randint(0, 10, size=(15, 2))  # Random points in 2-D
hull = ConvexHull(points)
for plot_id in (1, 2):
    fig, ax = plt.subplots(ncols=1, figsize=(5, 3))
    ax.plot(points[:, 0], points[:, 1], '.', color='k')
    if plot_id == 1:
        ax.set_title('Given points')
    else:
        ax.set_title('Convex hull')
        for simplex in hull.simplices:
            ax.plot(points[simplex, 0], points[simplex, 1], 'c')
        ax.plot(points[hull.vertices, 0], points[hull.vertices, 1], 'o', mec='r', color='none', lw=1, markersize=10)
    ax.set_xticks(range(10))
    ax.set_yticks(range(10))
    plt.show()