2.2 文本、注释、箭头
🚩常用函数如下：
| Pyplot函数 | API方法 | 描述 |
| text() | mpl.axes.Axes.text() | 在Axes对象的任意位置添加文字 |
| xlabel() | mpl.axes.Axes.set_xlabel() | 为X轴添加标签 |
| ylabel() | mpl.axes.Axes.set_ylabel() | 为Y轴添加标签 |
| title() | mpl.axes.Axes.set_title() | 为Axes对象添加标题 |
| legend() | mpl.axes.Axes.legend() | 为Axes对象添加图例 |
| annnotate() | mpl.axes.Axes.annotate() | 为Axes对象添加注释（箭头可选） |
| figtext() | mpl.figure.Figure.text() | 在Figure对象的任意位置添加文字 |
| suptitle() | mpl.figure.Figure.suptitle() | 为Figure对象添加中心化的标题 |
2.2.1 文本
import numpy as np import matplotlib.pyplot as plt # 字体属性 font = {'fontsize': 20, 'family': 'KaiTi', 'color': 'red', 'weight': 'bold'} # bold表示字体加粗 x = np.linspace(0.0, 5.0, 100) y = np.cos(2 * np.pi * x) * np.exp(-x) plt.figure(figsize = (9, 6)) plt.plot(x, y, 'k') # k代表黑色 # 视图的标题 plt.title('exponential decay', fontdict = font, pad = 20) # figure的大标题 plt.suptitle('指数衰减', y = 1.05, fontdict = font, fontsize = 30) # 向图片中绘制文本 plt.text(x = 2, y = 0.65, # 横纵坐标位置 s = r'$\cos(2 \pi t) \exp(-t)$', # 文本内容 fontsize = 25) # 文本大小 plt.xlabel('time (s)') plt.ylabel('voltage (mV)') plt.show()
2.2.2 箭头
import matplotlib.pyplot as plt import numpy # 随机生成数字，10行2列(x,y) loc = np.random.randint(0, 10,size = (10, 2)) plt.figure(figsize=(10, 10)) # 画图: loc[:, 0]:所有行都获取,索引0--->横坐标 # loc[:, 1]:所有行都获取,索引1--->纵坐标 # g*:g代表的是绿色,*代表的是点的形状是五角星 # ms = 20:点的大小 plt.plot(loc[:, 0], loc[:, 1], 'g*', ms = 20) plt.grid(True) # 路径 way = np.arange(10) # 0、1、2、...、9索引 np.random.shuffle(way) # 洗牌，打乱顺序 # 开始连点:0-->1-->2-->...-->9 # for 循环:少一个:10个点连9条线 for i in range(0, len(way) - 1): start = loc[way[i]] # 起点 end = loc[way[i + 1]] # 终点 # 画箭头: plt.arrow(start[0], start[1], # x = start[0], y = start[1]:起点的(x, y) end[0] - start[0], # 水平方向上移动的距离 end[1] - start[1], # 竖直方向上移动的距离 head_width = 0.2, lw = 2,# 箭头长度，箭尾线宽 length_includes_head = True) # 长度计算包含箭头箭尾 # 绘制编号:0 1 2 3... 8 plt.text(start[0], start[1], s = i, fontsize = 18, color = 'red') # 绘制编号:9 if i == len(way) - 2: plt.text(end[0], end[1], s = i + 1, fontsize = 18, color = 'red')
2.2.3 注释
import numpy as np import matplotlib.pyplot as plt # 数据创建 fig, ax = plt.subplots() x = np.arange(0.0, 5.0, 0.01) y = np.cos(2 * np.pi * x) line, = ax.plot(x, y, lw = 2) # 注释: ax.annotate('local max', # 文本内容 xy = (2, 1), # 箭头指向位置 xytext = (3, 1.5), # 文本位置 # 箭头属性 arrowprops = dict(facecolor = 'black', # 箭头的颜色 shrink = 0.05)) # 箭头两端收缩的百分比（占总长） ax.annotate('local min', xy = (2.5, -1), xytext = (4, -1.8), arrowprops = dict(facecolor = 'black', width = 2, # 箭头宽度 headwidth = 10, # 箭头头部宽度 headlength = 10, # 箭头头部长度 shrink = 0.1)) # 箭头两端收缩的百分比（占总长） ax.annotate('median', xy = (2.25, 0), xytext = (0.5, -1.8), arrowprops = dict(arrowstyle = '-|>'), # 箭头样式 # 按下 Shift+Tab查看提示:-|>:head_length=0.4,head_width=0.2 fontsize = 20) # y轴范围调为(-2, 2) ax.set_ylim(-2, 2)
2.2.4 注释箭头连接形状
import matplotlib.pyplot as plt def annotate_con_style(ax, connectionstyle): x1, y1 = 3,2 x2, y2 = 8,6 ax.plot([x1, x2], [y1, y2], ".") ax.annotate(text = '', xy = (x1, y1), # 相当于B点，arrow head xytext = (x2, y2), # 相当于A点，arrow tail arrowprops = dict(arrowstyle = '->', color = 'red', shrinkA = 5,shrinkB = 5, connectionstyle = connectionstyle)) ax.text(.05, 0.95, connectionstyle.replace(",", "\n"), transform = ax.transAxes, # 相对坐标 ha = "left", va = "top") # 指定对齐方式 # 常用箭头连接样式 fig, axs = plt.subplots(3, 5, figsize = (9, 6)) annotate_con_style(axs[0, 0], "angle3,angleA=90,angleB=0") annotate_con_style(axs[1, 0], "angle3,angleA=0,angleB=90") annotate_con_style(axs[2, 0], "angle3,angleA = 0,angleB=150") annotate_con_style(axs[0, 1], "arc3,rad=0.") annotate_con_style(axs[1, 1], "arc3,rad=0.3") annotate_con_style(axs[2, 1], "arc3,rad=-0.3") annotate_con_style(axs[0, 2], "angle,angleA=-90,angleB=180,rad=0") annotate_con_style(axs[1, 2], "angle,angleA=-90,angleB=180,rad=5") annotate_con_style(axs[2, 2], "angle,angleA=-90,angleB=10,rad=5") annotate_con_style(axs[0, 3], "arc,angleA=-90,angleB=0,armA=30,armB=30,rad=0") annotate_con_style(axs[1, 3], "arc,angleA=-90,angleB=0,armA=30,armB=30,rad=5") annotate_con_style(axs[2, 3], "arc,angleA=-90,angleB=0,armA=0,armB=40,rad=0") annotate_con_style(axs[0, 4], "bar,fraction=0.3") annotate_con_style(axs[1, 4], "bar,fraction=-0.3") annotate_con_style(axs[2, 4], "bar,angle=180,fraction=-0.2") for ax in axs.flat: # 设置轴域刻度 ax.set(xlim = (0, 10), ylim = (0, 10), xticks = [], yticks = [], aspect = 1) fig.tight_layout(pad = 0.2)
