我想改变数据框架结构[重复]

Question

这个问题在这里已有答案：

• Count occurences for each year in pandas dataframe based on subgroup 2回答

我目前的数据框架如下：

CREATED_DATE    STATE
02/03/15 0:00   Texas
02/03/15 0:00   Texas
02/03/17 16:19  Texas
02/03/15 16:19  Florida
02/03/16 16:19  Florida
02/03/16 16:19  Florida
02/03/15 16:19  Alabama
02/03/16 16:19  Alabama
02/03/15 16:19  North Carolina
02/03/15 16:19  North Carolina
02/03/16 16:19  North Carolina

我想把它改成：

STATE   2015    2016    2017
Texas   2   0   1
Florida 1   2   0
Alabama 1   1   0
North Carolina  2   1   0

Answer 1

尝试：

df.groupby(['STATE', df.CREATED_DATE.dt.year]).size().unstack(1, fill_value=0)