按星期幾分組熊貓

Question

  I have a dataframe,df 

        Index       eventName Count   pct
     2017-08-09       ABC     24     95.00%
     2017-08-09       CDE    140     98.50%
     2017-08-10       DEF    200     50.00%
     2017-08-11       CDE    150     99.30%
     2017-08-11       CDE    150     99.30%
     2017-08-16       DEF    200     50.00%
     2017-08-17       DEF    200     50.00%

我想通過對列pct中的值進行計數來按每日每周發生次數進行分組。 例如，我們現在有：

 2017-08-09 has 2 values in pct column  and  2017-08-16 has 1 value in pct, then we have Monday:3 
  2017-08-10  has 1 value and 2017-08-17 has 1 value,then we have Tuesday:2 and so on

那么結果數據框應如下所示：

    Index        Count   
 Monday            3
 Tuesday           2
 Wednesday         2

我試過了df2=df.groupby(pd.Grouper(freq='D')).size().sort_values(ascending=False)但它不是按星期幾分組，也不會轉換為單詞的日期索引

Answer 1

通過使用value_counts

df.Index=pd.to_datetime(df.Index)
df.Index.dt.weekday_name.value_counts()
Out[994]: 
Wednesday    3
Thursday     2
Friday       2
Name: Index, dtype: int64

Answer 2

Wen對value_counts的回答是好的，但沒有考慮pct列中NaN的可能性。

---

假設Index是指數，你可以調用groupby + count -

df.index = pd.to_datetime(df.index)
df.groupby(df.index.weekday_name).pct.count()

Index
Friday       2
Thursday     2
Wednesday    3
Name: pct, dtype: int64

要排序平日，轉換為pd.Categorical ，如圖所示這里 。

Answer 3

您可以使用：

df.rename(columns={'Index': 'New_name'}, inplace=True)

df['New_name'] = pd.to_datetime(df['New_name'])

df['Day_df'] = df['New_name'].dt.weekday_name

df.groupby(['Day_df']).count()