在Python中绘制分段函数

问题描述

我想使用Matplotlib在Python中从0到5绘制以下分段函数.

I would like to plot the following piecewise function in Python using Matplotlib, from 0 to 5.

f(x) = 1, x != 2; f(x) = 0, x = 2

在Python中...

In Python...

def f(x):
 if(x == 2): return 0
 else: return 1

使用NumPy创建一个数组

Using NumPy I create an array

x = np.arange(0., 5., 0.2)

    array([ 0. ,  0.2,  0.4,  0.6,  0.8,  1. ,  1.2,  1.4,  1.6,  1.8,  2. ,
        2.2,  2.4,  2.6,  2.8,  3. ,  3.2,  3.4,  3.6,  3.8,  4. ,  4.2,
        4.4,  4.6,  4.8])

我尝试过类似...

import matplotlib.pyplot as plt
plt.plot(x,f(x))

或者...

vecfunc = np.vectorize(f)
result = vecfunc(t)

或者...

def piecewise(x):
 if x == 2: return 0
 else: return 1

import matplotlib.pyplot as plt
x = np.arange(0., 5., 0.2)
plt.plot(x, map(piecewise, x))

ValueError: x and y must have same first dimension

但是我没有正确使用这些功能，现在只是随机猜测如何做到这一点.

But I am not using these functions correctly, and am now just randomly guessing how to do this.

一些答案​​开始到达那里...但是这些点已连接到绘图上的一条线中.我们如何绘制点?

Some answers are starting to get there... But the points are being connected into a line on the plot. How do we just plot the points?

推荐答案

import matplotlib.pyplot as plt
import numpy as np

def f(x):
 if(x == 2): return 0
 else: return 1

x = np.arange(0., 5., 0.2)

y = []
for i in range(len(x)):
   y.append(f(x[i]))

print x
print y

plt.plot(x,y,c='red', ls='', ms=5, marker='.')
ax = plt.gca()
ax.set_ylim([-1, 2])

plt.show()

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