先创建两组数据a和b
In [62]: a=pd.Series([np.nan,2.5,np.nan,3.5,4.5,np.nan],index=['f','e','d','c','b','a'])
In [63]: b=pd.Series([1,np.nan,3,4,
In [62]: a=pd.Series([np.nan,2.5,np.nan,3.5,4.5,np.nan],index=['f','e','d','c','b','a'])
In [63]: b=pd.Series([1,np.nan,3,4,