使用 pandas groupby 根據時間間隔獲取頻率計數

Question

我有一個 dataframe 如下圖所示

df = pd.DataFrame({'subject_id':[1,1,1,2,2,2],
              'start_time':['2130-03-25 18:51:47','2130-04-23 18:51:47','2130-04-23 18:51:47','2120-01-11 18:51:47','2120-01-11 18:51:47','2120-04-28 18:51:47'],
              'test_time':['2130-03-26 14:51:47','2130-04-24 18:51:47','2130-04-25 18:51:47','2121-02-26 18:51:47','2121-02-26 18:51:47','2120-04-28 19:51:47'],
              'test':['test1','test2','test2','test2','test3','test3']})
df['start_time'] = pd.to_datetime(df['start_time'])
df['test_time'] = pd.to_datetime(df['test_time'])

我想做的是

a) 從start_time開始每 24 小時獲取每個主題的測試次數。 測試時間可以從test_time列中找到

示例 - 24 小時，我的意思是0-24hours小時、 24-48hours小時、 48-72hours等。

我嘗試了以下

df['time_diff'] = (df.test_time - df.start_time) / pd.Timedelta(hours=1)
conditions = [
    (df['time_diff'] >= 0) & (df['time_diff'] <= 24),
    (df['time_diff'] >24 ) & (df['time_diff'] <= 48),
    (df['time_diff'] > 48) & (df['time_diff'] <= 72)]
choices = ['0-24hrs','24-48hrs','48-72hrs']
df['op'] = np.select(conditions, choices, default='Greater than 3 days')
df.groupby(['subject_id','test','op'])['test'].count()

但是，上面會產生格式不正確的 output。

我希望我的 output 如下所示

Answer 1

你可以只添加unstack

out = df.groupby(['subject_id','test','op'])['test'].count().unstack(fill_value=0).reset_index()
out
op  subject_id   test  0-24hrs  24-48hrs  Greater than 3 days
0            1  test1        1         0                    0
1            1  test2        1         1                    0
2            2  test2        0         0                    1
3            2  test3        1         0                    1