在Python中两个图形的交点，找到x值 [英] Intersection of two graphs in Python, find the x value

问题描述

让0< = x< =1.我有两列f和g分别为5000.现在我绘图:

Let 0 <= x <= 1. I have two columns f and g of length 5000 respectively. Now I plot:

plt.plot(x, f, '-')
plt.plot(x, g, '*')

我想找到曲线相交的点"x".我不想找到f和g的交集. 我可以这样简单地做到:

I want to find the point 'x' where the curve intersects. I don't want to find the intersection of f and g. I can do it simply with:

set(f) & set(g)

推荐答案

您可以将np.sign与np.diff和np.argwhere结合使用以获取线相交的点的索引(在这种情况下，点是[ 0, 149, 331, 448, 664, 743]):

You can use np.sign in combination with np.diff and np.argwhere to obtain the indices of points where the lines cross (in this case, the points are [ 0, 149, 331, 448, 664, 743]):

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 1000)
f = np.arange(0, 1000)
g = np.sin(np.arange(0, 10, 0.01) * 2) * 1000

plt.plot(x, f, '-')
plt.plot(x, g, '-')

idx = np.argwhere(np.diff(np.sign(f - g))).flatten()
plt.plot(x[idx], f[idx], 'ro')
plt.show()

首先，它使用np.sign计算f - g和相应的符号.应用np.diff会显示符号改变的所有位置(例如，线交叉).使用np.argwhere可以为我们提供准确的索引.

First it calculates f - g and the corresponding signs using np.sign. Applying np.diff reveals all the positions, where the sign changes (e.g. the lines cross). Using np.argwhere gives us the exact indices.

这篇关于在Python中两个图形的交点，找到x值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！