數據框前幾行均值

Question

我有以下數據框，並希望創建一個新列“ measurement_mean”，我希望新列中每一行的值都是所有先前“ Measurement”值的均值。

我怎樣才能做到這一點？

      Measurement  
   0          2.0  
   1          4.0  
   2          3.0  
   3          0.0  
   4        100.0  
   5          3.0  
   6          2.0  
   7          1.0  

Answer 1

使用pandas.Series.expanding

df[‘measurement_mean’] = df.Measurement.expanding().mean()

Answer 2

df['measurement_mean'] = df.Measurement.cumsum()/(df.index+1)