数据优化-多层索引 数据优化-多层索引

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数据优化-多层索引

多层索引

创建

环境：Jupyter

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['上半年','上半年','下半年','下半年'],
                                                    ['一季度','二季度','三季度','四季度']],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','白菜','牛肉','猪肉']])
display(a)

image-20211119143824001

设置索引的名称

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['上半年','上半年','下半年','下半年'],
                                                    ['一季度','二季度','三季度','四季度']],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','白菜','牛肉','猪肉']])
a.index.names=['年度','季度']
a.columns.names=['大类','小类']
display(a)

image-20211119151038703

from_arrays( )-from_tuples()

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python复制代码import numpy as np
import pandas as pd
index=pd.MultiIndex.from_arrays([['上半年','上半年','下半年','下半年'],['一季度','二季度','三季度','四季度']])
columns=pd.MultiIndex.from_tuples([('蔬菜','胡萝卜'),('蔬菜','白菜'),('肉类','牛肉'),('肉类','猪肉')])
a=pd.DataFrame(np.random.random(size=(4,4)),index=index,columns=columns)
display(a)

image-20211119151807886

笛卡儿积方式

from_product() 局限性较大

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python复制代码import pandas as pd
index = pd.MultiIndex.from_product([['上半年','下半年'],['蔬菜','肉类']])
a=pd.DataFrame(np.random.random(size=(4,4)),index=index)
display(a)

image-20211119152719775

多层索引操作

Series

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python复制代码import pandas as pd
a=pd.Series([1,2,3,4],index=[['a','a','b','b'],['c','d','e','f']])
print(a)
print('---------------------')
print(a.loc['a'])
print('---------------------')
print(a.loc['a','c'])

image-20211119153405471

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python复制代码import pandas as pd
a=pd.Series([1,2,3,4],index=[['a','a','b','b'],['c','d','e','f']])
print(a)
print('---------------------')
print(a.iloc[0])
print('---------------------')
print(a.loc['a':'b'])
print('---------------------')
print(a.iloc[0:2])

image-20211119153644981

DataFrame

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['上半年','上半年','下半年','下半年'],
                                                    ['一季度','二季度','三季度','四季度']],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','白菜','牛肉','猪肉']])
print(a)
print('--------------------')
print(a.loc['上半年','二季度'])
print('--------------------')
print(a.iloc[0])

image-20211119154634116

交换索引

swaplevel( )

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['2021','2021','2022','2022'],
                                                    ['一季度','二季度','三季度','四季度']],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','白菜','牛肉','猪肉']])
a.index.names=['年度','季度']
print(a)
print('--------------------')
print(a.swaplevel('年度','季度'))

image-20211119160130816

索引排序

sort_index( )

level：指定根据哪一层进行排序，默认为最层

inplace：是否修改原数据。默认为False

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['2021','2021','2022','2022'],
                                                    [1,3,2,4]],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','白菜','牛肉','猪肉']])
a.index.names=['年度','季度']
print(a)
print('--------------------')
print(a.sort_index())
print('--------------------')
print(a.sort_index(level=1))

image-20211119160714806

索引堆叠

stack( )

将指定层级的列转换成行

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['2021','2021','2022','2022'],
                                                    [1,3,2,4]],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','胡萝卜','牛肉','牛肉']])
print(a)
print('--------------------')
print(a.stack(0))
print('--------------------')
print(a.stack(-1))

image-20211119161612152

取消堆叠

unstack( )

将指定层级的行转换成列

fill_value：指定填充值。

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['2021','2021','2022','2022'],
                                                    [1,3,2,4]],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','胡萝卜','牛肉','牛肉']])
print(a)
print('--------------------')
a=a.stack(0)
print(a)
print('--------------------')
print(a.unstack(-1))

image-20211119162659896

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python复制代码import numpy as np
import pandas as pd
a=pd.DataFrame(np.random.random(size=(4,4)),index=[['2021','2021','2022','2022'],
                                                    [1,3,2,4]],
              columns=[['蔬菜','蔬菜','肉类','肉类'],['胡萝卜','胡萝卜','牛肉','牛肉']])
print(a)
print('--------------------')
a=a.stack(0)
print(a)
print('--------------------')
print(a.unstack(0,fill_value='0'))

image-20211119162928207

本文转载自: 掘金

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