从数据中现有的std列添加标准偏差栏？

如何解决从数据中现有的std列添加标准偏差栏？

我正在基于以下数据绘制图表（仅头部）：

Date    noctiluca_ave   density_ave density_sd
0   2018-03-07  2.0 1027.514332 0.091766
1   2018-03-14  4.0 1027.339988 0.285309
2   2018-03-21  1.0 1027.346413 0.183336
3   2018-03-31  1.0 1027.372996 0.170423
4   2018-04-07  0.0 1027.292119 0.187385

如何将标准偏差（'density_sd'）条形图添加到density_ave线？

fig,ax = plt.subplots(figsize=(10,10))
ax.plot(hydro_weekly2 ['Date'],hydro_weekly2 ['density_ave'],label='density weekly ave',color='purple')
ax2=ax.twinx()
ax2.plot(hydro_weekly2['Date'],hydro_weekly2['noctiluca_ave'],label='noctiluca abundance',color='r')
ax.set_ylabel('Density')
ax.set_xlabel('Date')
ax2.set_ylabel('Noctiluca abundance/cells per m3')
ax.set(title="Noctiluca Abundance and Density 2018")


lines,labels = ax.get_legend_handles_labels()
lines2,labels2 = ax2.get_legend_handles_labels()
ax2.legend(lines + lines2,labels + labels2,loc="upper left")

enter image description here

解决方法

您可以将ax.plot替换为ax.errorbar()，也可以使用ax.fill_between()来显示彩色带。

以下是一个包含玩具数据并将两种方法结合在一起的示例：

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

N = 20
dates = pd.date_range('2018-03-07',periods=N,freq='W-WED')
hydro_weekly2 = pd.DataFrame({'Date': dates,'noctiluca_ave': np.random.randint(0,14000,N),'density_ave': 1027 + np.random.randn(N).cumsum() / 5,'density_sd': 0.1 + np.abs(np.random.randn(N) / 5)})
fig,ax = plt.subplots(figsize=(10,10))
ax.errorbar(hydro_weekly2['Date'],hydro_weekly2['density_ave'],yerr=hydro_weekly2['density_sd'],label='density weekly ave',color='purple')
ax.fill_between(hydro_weekly2['Date'],hydro_weekly2['density_ave'] - hydro_weekly2['density_sd'],hydro_weekly2['density_ave'] + hydro_weekly2['density_sd'],color='purple',alpha=0.3)
ax2 = ax.twinx()
ax2.plot(hydro_weekly2['Date'],hydro_weekly2['noctiluca_ave'],label='noctiluca abundance',color='r')
ax.set_ylabel('Density')
ax.set_xlabel('Date')
ax2.set_ylabel('Noctiluca abundance/cells per m3')
ax.set(title="Noctiluca Abundance and Density 2018")
plt.show()

自此，您正在处理dataframe。这是用density_sd绘图显示pandas条的另一种方法。该方法也适用于barplot。

import pandas as pd
import matplotlib.pyplot as plt

df = pd.read_csv('test.csv',parse_dates=['Date'],index_col=0)

ax = df['density_ave'].plot(yerr=df['density_sd'].T)
df['noctiluca_ave'].plot(yerr=df['density_sd'].T,secondary_y=True,ax=ax) 
## added errorbar in the secondary y as well.
plt.show()

输出：