numpy的两条线的交点[重复]

Question

我想使用 numpy 在 python 中获得两条线的交点。我写了一段代码，但我无法完成代码。我有一条由 numpy 读取并由 matplotlib 绘制的 1000 点曲线。另外，我绘制了 y=0 线，目前，我想知道第一条曲线与 y = 0 线的交点数。如下图所示

代码如下：

import matplotlib.pyplot as plt
import numpy as np

#ll = np.linspace(min(x),max(x),1696)


with open('file1.txt', 'r') as f:
    lines = f.readlines()
    x = [float(line.split()[0]) for line in lines]
    y = [float(line.split()[1]) for line in lines]
    a = np.array(y)
    b = np.where (y==0)
print(b)

我们将不胜感激。

Answer 1

试试这个：

import numpy as np

a = np.random.random(20) * 2         # 20 random float numbers between 0 and 2
b = np.ones_like(a, dtype=np.float)  # 20 numbers equal to 1

epsilon = 0.05
solution = np.abs(a-b) < epsilon  # index of items in `a` that are close enough (epsilon) to `b`

print(solution)

您也可以使用：

solution = np.isclose(a,b, rtol=epsilon)

Answer 2

您正在尝试做的只是一个过零问题。保证过零计数的蛮力方法。从技术上讲，也可用于检查任何线路。只需要稍微改变条件语句。假设处于 0 处不算作过零。请注意，这些点需要是为了使它起作用。

y = [0,1,2,3,2,1,0,-1,0,0,1,-2,5,-6,0]
counter = 0
last_non_zero = None #buffer for handling zeroes
for i in range(len(y)-1):
    if y[i] == 0 and i == 0:
        pass
        #First item we ignore for zero crossing if start at 0
    elif y[i] == 0 and i!=0:
        if last_non_zero is not None and last_non_zero*y[i+1]<0
            counter += 1
            #handles 0 values 
    else:
        if y[i] * y[i+1] <0:
            counter +=1 #Condition for last value unnecessary since n*0 = 0 which is not <0
    if y[i] != 0:
        last_non_zero = y[i] #replace buffer

使用 ++ = +、--=+、+-=-、-+=- 的逻辑，其中最后两个是过零。