在 pandas 中使用 groupby 绘制累积和

Question

I'm missing something really obvious or simply doing this wrong. I have two dataframes of similar structure and I'm trying to plot a time-series of the cumulative sum of one column from both. The dataframes are indexed by date:

df1
              value
2020-01-01    2435
2020-01-02    12847
...
2020-10-01    34751

The plot should be grouped by month and be a cumulative sum of the whole time range. I've tried:

line1 = df1.groupby(pd.Grouper(freq='1M')).value.cumsum()
line2 = df2.groupby(pd.Grouper(freq='1M')).value.cumsum()

and then plot, but it resets after each month. How can I change this?

Answer 1

I am guessing you want to group and take the mean or something to represent the cumulative value for each month, and plot:

df1 = pd.DataFrame({'value':np.random.randint(100,200,366)},
                   index=pd.date_range(start='1/1/2018', end='1/1/2019'))

df1.cumsum().groupby(pd.Grouper(freq='1M')).mean().plot()