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# 2.1.4.5.GroupBy

## GroupBy的概念

* 讓table中有相同ID的row可以成組

## 操作

1. 產生groupby物件

   ```
    import numpy as np
    import pandas as pd
    data = {'Company': ['GooG', 'GooG', 'Att', 'Att'],
       'Person': ['Sam', 'Mike', 'Ray', 'Neil'],
       'Sales': [200, 100, 130, 500]}
    df = pd.DataFrame(data)
    byComp = df.GroupBy('Company')
   ```
2. 對groupby物件使用aggregate function

   ```
    byComp.mean()
    byComp.sum()
    byComp.std()
    byComp.count()
    byComp.min()
    byComp.describe()
    byComp.describe().transpose()
   ```