Python中的 Matplotlib.pyplot.stem()

Matplotlib 是Python中用于数组二维图的可视化库。 Matplotlib 是一个基于 NumPy 数组的多平台数据可视化库，旨在与更广泛的 SciPy 堆栈一起使用。

matplotlib.pyplot.stem()

matplotlib.pyplot.stem()创建茎图。 Stem plot在图表下覆盖的每个 x 位置绘制从基线到 y 的垂直线，并在那里放置一个标记。

Syntax: stem([x, ] y, linefmt=None, markerfmt=None, basefmt=None)

Parameters:

• x (array-like, optional): The x-positions of the stems. Default: (0, 1, …, len(y) – 1).
• y (array-like): The y-values of the stem heads.
• linefmt (str, optional): A string defining the properties of the vertical lines. Usually, this will be a color or a color and a linestyle:
  • ‘-‘: solid line
  • ‘–‘: dashed line
  • ‘-.’: dash-dot line
  • ‘:’ dotted line

  Note: While it is technically possible to specify valid formats other than color or color and linestyle (e.g. ‘rx’ or ‘-.’), this is beyond the intention of the method and will most likely not result in a reasonable plot.

• markerfmt (str, optional): A string defining the properties of the markers at the stem heads. Default: ‘C0o’, i.e. filled circles with the first color of the color cycle.
• basefmt (str, optional): A format string defining the properties of the baseline.
  Default: ‘C3-‘ (‘C2-‘ in classic mode).
• bottom (float, optional, default: 0): The y-position of the baseline.
• label (str, optional, default: None): The label to use for the stems in legends.
• use_line_collection (bool, optional, default: False): If True, store and plot the stem lines as a LineCollection instead of individual lines. This significantly increases performance, and will become the default option in Matplotlib 3.3. If False, defaults to the old behavior of using a list of Line2D objects.

Returns :

container: StemContainer

The container may be treated like a tuple
(markerline, stemlines, baseline)

示例 #1：默认绘图

Stem 绘制从基线到 y 坐标的垂直线，并在尖端放置一个标记。

# importing libraries
import matplotlib.pyplot as plt
import numpy as np
  
x = np.linspace(0.1, 2 * np.pi, 41)
y = np.exp(np.sin(x))
  
plt.stem(x, y, use_line_collection = True)
plt.show()

输出 ：
示例 #2：
基线的位置可以使用底部进行调整。参数linefmt、markerfmt和basefmt控制绘图的基本格式属性。但是，与plot相比，并非所有属性都可以通过关键字参数进行配置。对于更高级的控制，请调整pyplot返回的线对象。

# importing libraries
import random
import matplotlib.pyplot as plt
  
x = np.linspace(0.1, 2 * np.pi, 41)
y = np.exp(np.sin(x))
  
markerline, stemlines, baseline = plt.stem(
    x, y, linefmt ='grey', markerfmt ='D',
    bottom = 1.1, use_line_collection = True)
  
markerline.set_markerfacecolor('none')
plt.show()

输出：