如何使用matplotlib检测是否存在交集？

Question

我正在使用 matplotlib 绘制这两个折线图。但是，只有有时我的图表才会有交集。如何检测我的折线图是否有交点？

df = pd.read_csv("test.csv")

df2 = pd.read_csv("test2.csv")

x1 = df['A'].tolist()
x1 = np.array(x1)

y1 = df['D'].tolist()
y1 = np.array(y1)

x2 = df2['X'].tolist()
x2 = np.array(x2)

y2 = df2['Y'].tolist()
y2 = np.array(y2)

plt.plot(x1,y1)
plt.plot(x2,y2)
plt.show()

Answer 1

您可以计算交点索引：

idx = np.argwhere(np.diff(np.sign(y1 - y2))).flatten()

如果有一个或多个交点，idx是一个交点列表，否则是一个空列表。

一个或多个路口

import numpy as np
import matplotlib.pyplot as plt

x1 = np.linspace(0, 10, 1000)
x2 = np.linspace(-2, 5, 1000)
y1 = np.sin(x1)
y2 = np.cos(x2) + 1

idx = np.argwhere(np.diff(np.sign(y1 - y2))).flatten()

fig, ax = plt.subplots()

ax.plot(x1, y1, 'blue')
ax.plot(x2, y2, 'red')

plt.show()

print(len(idx))
2

无交集

import numpy as np
import matplotlib.pyplot as plt

x1 = np.linspace(0, 10, 1000)
x2 = np.linspace(-2, 5, 1000)
y1 = np.sin(x1)
y2 = np.cos(x2) + 2

idx = np.argwhere(np.diff(np.sign(y1 - y2))).flatten()

fig, ax = plt.subplots()

ax.plot(x1, y1, 'blue')
ax.plot(x2, y2, 'red')

plt.show()

print(len(idx))
0

Answer 2

如果 y 值在某个点相互交叉，此代码将打印 'intersect'。

mark = y1[0]-y2[0]

for i in range(len(y1)):
    if mark > 0:
        if y1[i]-y2[i] < 0:
        print('intersect')
    elif mark < 0:
        if y1[i]-y2[i] > 0:
            print('intersect')

如何使用matplotlib检测是否存在交集？

How to detect if there is intersection using matplotlib?

python

plot

visualization

numpy

matplotlib