线图开始和结尾处的标记

Question

我有5个数据集，这些数据集由“帧”组成的数千个X和Y坐标创建5个轨迹图。我想为每个情节标记第一个和最后一个坐标，但很难弄清楚。我正在使用木星笔记本。

mean_pos1 = gr1.mean()
mean_pos2 = gr2.mean()
mean_pos3 = gr3.mean()
mean_pos4 = gr4.mean()
mean_pos5 = gr5.mean()
plt.figure()

xlim=(200, 1500)
ylim=(0, 1200)
ax1 = mean_pos1.plot(x='x', y='y',color='blue',label='Dolphin A'); ax1.set_title('mean trajectory'); 
ax2 = mean_pos2.plot(x='x', y='y',color='red',label='Dolphin B'); ax2.set_title('mean trajectory');
ax3 = mean_pos3.plot(x='x', y='y',color='green',label='Dolphin C'); ax3.set_title('mean trajectory');
ax4 = mean_pos4.plot(x='x', y='y',color='magenta',label='Dolphin D'); ax4.set_title('mean trajectory');
ax5 = mean_pos5.plot(x='x', y='y',color='cyan',label='Dolphin E'); ax5.set_title('mean trajectory');
ax1.set_xlim(xlim)
ax1.set_ylim(ylim)
ax2.set_xlim(xlim)
ax2.set_ylim(ylim)
ax3.set_xlim(xlim)
ax3.set_ylim(ylim)
ax4.set_xlim(xlim)
ax4.set_ylim(ylim)
ax5.set_xlim(xlim)
ax5.set_ylim(ylim)


plt.show()

它们的输出看起来像这样：

Answer 1

markevery = [0，-1]。这将标记放置在数据的所需索引（因此-1指的是最后一个元素）。这样，您就不需要单独的绘图命令，标记在传说中正确显示：

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

df = pd.DataFrame({'x': np.random.normal(3,0.2,10), 'y': np.random.normal(5,0.3,10)})

fig, ax = plt.subplots()

df.plot(x='x', y='y', ax=ax, markevery=[0,-1], marker='o',markerfacecolor='r',markeredgecolor='r')

Answer 2

使用散点方法，通过从x和y系列中获取第一个和最后一个元素，将标记分别绘制在同一轴上：

import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

df = pd.DataFrame({'x': np.random.normal(3,0.2,10), 'y': np.random.normal(5,0.3,10)})

fig, ax = plt.subplots()

df.plot(x='x', y='y', ax=ax)

ax.scatter(df['x'].iloc[0], df['y'].iloc[0], marker='o', color='red')
ax.scatter(df['x'].iloc[-1], df['y'].iloc[-1], marker='o', color='red')

plt.show()