使用 matplotlib 将平均值和 3*std 添加到散点图

Question

I've got a scatter plot and want add a straight line for mean, 3*std+mean and 3*std-mean. I seem to have the mean plotting but can't work out the std! Thanks

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

    for element in df_na.loc[:, 'Ag_ppb':'Zr_ppb']:
        temp_df = df_na.loc[:, ['Date', element]].dropna()
        fig =plt.figure()
        plt.scatter(temp_df['Date'], temp_df[element],c='black',s=10)
        plt.plot(temp_df['Date'],[df_na[element].mean()]*len(x))
        plt.xlabel('Date')
        plt.xticks(rotation =90, fontsize=5)
        plt.ylabel(element)
        plt.show() 

Answer 1

你想使用 dataframe.std()：

df_na.std(axis=0,skipna=True)[element]

Answer 2

So I incorporated the above which works, see below:

plt.plot(temp_df['Date'],[temp_df[element].mean(axis=0,skipna=True)]*len(x), c='red',label='Mean')

but the following won't plot the 3* std + mean .

 plt.plot(temp_df['Date'],[temp_df[element].mean()]+[temp_df[element].std(axis=0,skipna=True)*3]*len(x),label='3xstd') 

Answer 3

以上工作但不将平均值添加到 3*std 不会绘制为一条线。