在 Matplotlib 中绘制一条水平线

Matplotlib 是一个流行的用于绘图的Python库，它提供了一个面向对象的 API 来渲染 GUI 绘图

绘制水平线相当简单，使用axhline()

matplotlib 库的 pyplot 模块中的axhline()函数用于在轴上添加一条水平线。

Syntax: matplotlib.pyplot.axhline(y, color, xmin, xmax, linestyle)

Parameters:

• y: Position on Y axis to plot  the line, It accepts integers.
• xmin and xmax: scalar, optional, default: 0/1.  It plots the line in the given range
• color: color for the line, It accepts  a string. eg ‘r’ or ‘b’ .
• linestyle: Specifies the type of line, It accepts a string. eg ‘-‘, ‘–‘, ‘-.’, ‘:’, ‘None’, ‘ ‘, ”, ‘solid’, ‘dashed’, ‘dashdot’, ‘dotted’

绘制一条水平线

Python3

# importing library
import matplotlib.pyplot as plt
  
# specifying horizontal line type
plt.axhline(y = 0.5, color = 'r', linestyle = '-')
  
# rendering the plot
plt.show()

输出：

绘制多条水平线

要绘制多条水平线，请多次使用 axhline() 方法。

Python

# importing the module
import matplotlib.pyplot as plt
  
# plotting line within the given range
plt.axhline(y = .5, xmin = 0.25, xmax = 0.9)
  
# line colour is blue
plt.axhline(y = 3, color = 'b', linestyle = ':')
  
# line colour is white
plt.axhline(y = 1, color = 'w', linestyle = '--')
  
# line colour is red
plt.axhline(y = 2, color = 'r', linestyle = 'dashed')    
    
# adding axis labels    
plt.xlabel('x - axis')
plt.ylabel('y - axis')
  
# displaying the plot
plt.show()

输出：

添加图例

可以使用legend()函数添加图例。

蟒蛇3

# importing the module
import matplotlib.pyplot as plt
  
# plotting line within the given range
plt.axhline(y = .5, xmin = 0.25, xmax = 0.9)
  
# line colour is blue
plt.axhline(y = 3, color = 'b', linestyle = ':', label = "blue line")
  
# line colour is white
plt.axhline(y = 1, color = 'w', linestyle = '--', label = "white line")
  
# line colour is red
plt.axhline(y = 2, color = 'r', linestyle = 'dashed', label = "red line")    
    
# adding axis labels    
plt.xlabel('x - axis')
plt.ylabel('y - axis')
  
# plotting the legend
plt.legend(bbox_to_anchor = (1.0, 1), loc = 'upper center')
  
# displaying the plot
plt.show()

输出：