第6章 深入pandas：数据处理 117
6.1 数据准备 117
合并
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#merge是两个dataframe共同包含的项import numpy as npimport pandas as pdframe1 = pd.DataFrame( {‘id‘:[‘ball‘,‘pencil‘,‘pen‘,‘mug‘,‘ashtray‘], ‘price‘: [12.33,11.44,33.21,13.23,33.62]})print(frame1)print()frame2 = pd.DataFrame( {‘id‘:[‘pencil‘,‘pencil‘,‘ball‘,‘pen‘],‘color‘: [‘white‘,‘red‘,‘red‘,‘black‘]})print(frame2)print()temp = pd.merge(frame1,frame2)print(temp)
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id price
0 ball 12.33
1 pencil 11.44
2 pen 33.21
3 mug 13.23
4 ashtray 33.62
color id
0 white pencil
1 red pencil
2 red ball
3 black pen
id price color
0 ball 12.33 red
1 pencil 11.44 white
2 pencil 11.44 red
3 pen 33.21 black
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frame1 = pd.DataFrame( {‘id‘:[‘ball‘,‘pencil‘,‘pen‘,‘mug‘,‘ashtray‘], ‘color‘: [‘white‘,‘red‘,‘red‘,‘black‘,‘green‘], ‘brand‘: [‘OMG‘,‘ABC‘,‘ABC‘,‘POD‘,‘POD‘]})print(frame1)print()frame2 = pd.DataFrame( {‘id‘:[‘pencil‘,‘pencil‘,‘ball‘,‘pen‘], ‘brand‘: [‘OMG‘,‘POD‘,‘ABC‘,‘POD‘]})print(frame2)print()
temp = pd.merge(frame1,frame2)print(temp)print()
temp = pd.merge(frame1,frame2,on=‘id‘)print(temp)print()
temp = pd.merge(frame1,frame2,on=‘brand‘)print(temp)
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brand color id
0 OMG white ball
1 ABC red pencil
2 ABC red pen
3 POD black mug
4 POD green ashtray
brand id
0 OMG pencil
1 POD pencil
2 ABC ball
3 POD pen
Empty DataFrame
Columns: [brand, color, id]
Index: []
brand_x color id brand_y
0 OMG white ball ABC
1 ABC red pencil OMG
2 ABC red pencil POD
3 ABC red pen POD
brand color id_x id_y
0 OMG white ball pencil
1 ABC red pencil ball
2 ABC red pen ball
3 POD black mug pencil
4 POD black mug pen
5 POD green ashtray pencil
6 POD green ashtray pen
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print(frame1)print()frame2.columns = [‘brand‘,‘sid‘]print(frame2)print()
temp = pd.merge(frame1, frame2, left_on=‘id‘, right_on=‘sid‘)print(temp)
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brand color id
0 OMG white ball
1 ABC red pencil
2 ABC red pen
3 POD black mug
4 POD green ashtray
brand sid
0 OMG pencil
1 POD pencil
2 ABC ball
3 POD pen
brand_x color id brand_y sid
0 OMG white ball ABC ball
1 ABC red pencil OMG pencil
2 ABC red pencil POD pencil
3 ABC red pen POD pen
123
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frame2.columns = [‘brand‘,‘id‘]temp = pd.merge(frame1,frame2,on=‘id‘)print(temp)
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brand_x color id brand_y
0 OMG white ball ABC
1 ABC red pencil OMG
2 ABC red pencil POD
3 ABC red pen POD
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temp = pd.merge(frame1,frame2,on=‘id‘,how=‘outer‘)print(temp)
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brand_x color id brand_y
0 OMG white ball ABC
1 ABC red pencil OMG
2 ABC red pencil POD
3 ABC red pen POD
4 POD black mug NaN
5 POD green ashtray NaN
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temp = pd.merge(frame1,frame2,on=‘id‘,how=‘left‘)print(temp)
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brand_x color id brand_y
0 OMG white ball ABC
1 ABC red pencil OMG
2 ABC red pencil POD
3 ABC red pen POD
4 POD black mug NaN
5 POD green ashtray NaN
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temp = pd.merge(frame1,frame2,on=‘id‘,how=‘right‘)print(temp)
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brand_x color id brand_y
0 OMG white ball ABC
1 ABC red pencil OMG
2 ABC red pencil POD
3 ABC red pen POD
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temp = pd.merge(frame1,frame2,on=[‘id‘,‘brand‘],how=‘outer‘)print(temp)
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brand color id
0 OMG white ball
1 ABC red pencil
2 ABC red pen
3 POD black mug
4 POD green ashtray
5 OMG NaN pencil
6 POD NaN pencil
7 ABC NaN ball
8 POD NaN pen
根据索引合并
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temp = pd.merge(frame1,frame2,right_index=True, left_index=True) print(temp)
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brand_x color id_x brand_y id_y
0 OMG white ball OMG pencil
1 ABC red pencil POD pencil
2 ABC red pen ABC ball
3 POD black mug POD pen
123
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frame2.columns = [‘brand2‘,‘id2‘]temp = frame1.join(frame2)print(temp)
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brand color id brand2 id2
0 OMG white ball OMG pencil
1 ABC red pencil POD pencil
2 ABC red pen ABC ball
3 POD black mug POD pen
4 POD green ashtray NaN NaN
6.2 拼接 122
12
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array1 = np.arange(9).reshape((3,3))array1
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array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
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array2 = np.arange(9).reshape((3,3))+6array2
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array([[ 6, 7, 8],
[ 9, 10, 11],
[12, 13, 14]])
1
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np.concatenate([array1,array2],axis=1)
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array([[ 0, 1, 2, 6, 7, 8],
[ 3, 4, 5, 9, 10, 11],
[ 6, 7, 8, 12, 13, 14]])
1
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np.concatenate([array1,array2],axis=0)
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array([[ 0, 1, 2],
[ 3, 4, 5],
[ 6, 7, 8],
[ 6, 7, 8],
[ 9, 10, 11],
[12, 13, 14]])
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ser1 = pd.Series(np.random.rand(4), index=[1,2,3,4])ser1
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1 0.480270
2 0.440535
3 0.378281
4 0.799113
dtype: float64
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ser2 = pd.Series(np.random.rand(4), index=[5,6,7,8])ser2
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5 0.134120
6 0.703728
7 0.657262
8 0.020803
dtype: float64
12
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temp = pd.concat([ser1,ser2])print(temp)
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1 0.444507
2 0.690626
3 0.595412
4 0.030619
5 0.134120
6 0.703728
7 0.657262
8 0.020803
dtype: float64
12
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ser3 = pd.concat([ser1,ser2],axis=1)print(ser3)
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0 1
1 0.444507 NaN
2 0.690626 NaN
3 0.595412 NaN
4 0.030619 NaN
5 NaN 0.134120
6 NaN 0.703728
7 NaN 0.657262
8 NaN 0.020803
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temp = pd.concat([ser1,ser3],axis=1,join=‘inner‘)print(temp)
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0 0 1
1 0.444507 0.444507 NaN
2 0.690626 0.690626 NaN
3 0.595412 0.595412 NaN
4 0.030619 0.030619 NaN
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temp = pd.concat([ser1,ser2], keys=[1,2])print(temp)
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1 1 0.444507
2 0.690626
3 0.595412
4 0.030619
2 5 0.134120
6 0.703728
7 0.657262
8 0.020803
dtype: float64
12
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temp = pd.concat([ser1,ser2], axis=1, keys=[1,2])print(temp)
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1 2
1 0.444507 NaN
2 0.690626 NaN
3 0.595412 NaN
4 0.030619 NaN
5 NaN 0.134120
6 NaN 0.703728
7 NaN 0.657262
8 NaN 0.020803
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frame1 = pd.DataFrame(np.random.rand(9).reshape(3,3), index=[1,2,3], columns=[‘A‘,‘B‘,‘C‘])print(frame1)print()frame2 = pd.DataFrame(np.random.rand(9).reshape(3,3), index=[4,5,6], columns=[‘A‘,‘B‘,‘C‘])print(frame2)print()temp = pd.concat([frame1, frame2])print(temp)
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A B C
1 0.918894 0.884497 0.451266
2 0.990586 0.412664 0.289380
3 0.058831 0.746895 0.911668
A B C
4 0.256936 0.837374 0.677940
5 0.379119 0.453602 0.858519
6 0.832512 0.736023 0.583485
A B C
1 0.918894 0.884497 0.451266
2 0.990586 0.412664 0.289380
3 0.058831 0.746895 0.911668
4 0.256936 0.837374 0.677940
5 0.379119 0.453602 0.858519
6 0.832512 0.736023 0.583485
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temp = pd.concat([frame1, frame2], axis=1)print(temp)
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A B C A B C
1 0.918894 0.884497 0.451266 NaN NaN NaN
2 0.990586 0.412664 0.289380 NaN NaN NaN
3 0.058831 0.746895 0.911668 NaN NaN NaN
4 NaN NaN NaN 0.256936 0.837374 0.677940
5 NaN NaN NaN 0.379119 0.453602 0.858519
6 NaN NaN NaN 0.832512 0.736023 0.583485
6.2.1 组合 124
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ser1 = pd.Series(np.random.rand(5),index=[1,2,3,4,5])print(ser1)print()ser2 = pd.Series(np.random.rand(4),index=[2,4,5,6])print(ser2)print()temp = ser1.combine_first(ser2)print(temp)
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1 0.598971
2 0.143975
3 0.080446
4 0.437893
5 0.033583
dtype: float64
2 0.326416
4 0.732483
5 0.476231
6 0.468597
dtype: float64
1 0.598971
2 0.143975
3 0.080446
4 0.437893
5 0.033583
6 0.468597
dtype: float64
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temp = ser2.combine_first(ser1)print(temp)
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1 0.598971
2 0.326416
3 0.080446
4 0.732483
5 0.476231
6 0.468597
dtype: float64
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temp = ser1[:3].combine_first(ser2[:3])print(temp)
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1 0.598971
2 0.143975
3 0.080446
4 0.732483
5 0.476231
dtype: float64
6.2.2 轴向旋转 125
按等级索引旋转
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frame1 = pd.DataFrame(np.arange(9).reshape(3,3),index=[‘white‘,‘black‘,‘red‘],columns=[‘ball‘,‘pen‘,‘pencil‘])print(frame1)ser5 = frame1.stack()ser5
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ball pen pencil
white 0 1 2
black 3 4 5
red 6 7 8
white ball 0
pen 1
pencil 2
black ball 3
pen 4
pencil 5
red ball 6
pen 7
pencil 8
dtype: int32
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temp = ser5.unstack()print(temp)
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ball pen pencil
white 0 1 2
black 3 4 5
red 6 7 8
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temp = ser5.unstack(0)print(temp)
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white black red
ball 0 3 6
pen 1 4 7
pencil 2 5 8
从长格式向宽格式旋转
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longframe = pd.DataFrame({ ‘color‘:[‘white‘,‘white‘,‘white‘, ‘red‘,‘red‘,‘red‘, ‘black‘,‘black‘,‘black‘], ‘item‘:[‘ball‘,‘pen‘,‘mug‘, ‘ball‘,‘pen‘,‘mug‘, ‘ball‘,‘pen‘,‘mug‘], ‘value‘: np.random.rand(9)})print(longframe)
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color item value
0 white ball 0.905908
1 white pen 0.476735
2 white mug 0.569165
3 red ball 0.483042
4 red pen 0.663438
5 red mug 0.866178
6 black ball 0.752131
7 black pen 0.616940
8 black mug 0.713100
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wideframe = longframe.pivot(‘color‘,‘item‘)print(wideframe)
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value
item ball mug pen
color
black 0.752131 0.713100 0.616940
red 0.483042 0.866178 0.663438
white 0.905908 0.569165 0.476735
6.2.3 删除 127
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frame1 = pd.DataFrame(np.arange(9).reshape(3,3), index=[‘white‘,‘black‘,‘red‘], columns=[‘ball‘,‘pen‘,‘pencil‘])print(frame1)del frame1[‘ball‘]print(frame1)temp = frame1.drop(‘white‘)print(temp)print(frame1)
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ball pen pencil
white 0 1 2
black 3 4 5
red 6 7 8
pen pencil
white 1 2
black 4 5
red 7 8
pen pencil
black 4 5
red 7 8
pen pencil
white 1 2
black 4 5
red 7 8
6.3 数据转换 128
6.3.1 删除重复元素 128
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dframe = pd.DataFrame({ ‘color‘: [‘white‘,‘white‘,‘red‘,‘red‘,‘white‘], ‘value‘: [2,1,3,3,2]})print(dframe)temp = dframe.duplicated()print(temp)temp = dframe[dframe.duplicated()]print(temp)
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color value
0 white 2
1 white 1
2 red 3
3 red 3
4 white 2
0 False
1 False
2 False
3 True
4 True
dtype: bool
color value
3 red 3
4 white 2
6.3.2 映射 129
用映射替换元素
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frame = pd.DataFrame({ ‘item‘:[‘ball‘,‘mug‘,‘pen‘,‘pencil‘,‘ashtray‘], ‘color‘:[‘white‘,‘rosso‘,‘verde‘,‘black‘,‘yellow‘],‘price‘:[5.56,4.20,1.30,0.56,2.75]})print(frame)newcolors = { ‘rosso‘: ‘red‘, ‘verde‘: ‘green‘ }temp = frame.replace(newcolors)print(temp)
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color item price
0 white ball 5.56
1 rosso mug 4.20
2 verde pen 1.30
3 black pencil 0.56
4 yellow ashtray 2.75
color item price
0 white ball 5.56
1 red mug 4.20
2 green pen 1.30
3 black pencil 0.56
4 yellow ashtray 2.75
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ser = pd.Series([1,3,np.nan,4,6,np.nan,3])print(ser)temp = ser.replace(np.nan,0)print(temp)
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0 1.0
1 3.0
2 NaN
3 4.0
4 6.0
5 NaN
6 3.0
dtype: float64
0 1.0
1 3.0
2 0.0
3 4.0
4 6.0
5 0.0
6 3.0
dtype: float64
用映射添加元素
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frame = pd.DataFrame({ ‘item‘:[‘ball‘,‘mug‘,‘pen‘,‘pencil‘,‘ashtray‘], ‘color‘:[‘white‘,‘red‘,‘green‘,‘black‘,‘yellow‘]})print(frame)price = { ‘ball‘ : 5.56, ‘mug‘ : 4.20, ‘bottle‘ : 1.30, ‘scissors‘ : 3.41, ‘pen‘ : 1.30, ‘pencil‘ : 0.56, ‘ashtray‘ : 2.75 }frame[‘price‘] = frame[‘item‘].map(price)print(frame)
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color item
0 white ball
1 red mug
2 green pen
3 black pencil
4 yellow ashtray
color item price
0 white ball 5.56
1 red mug 4.20
2 green pen 1.30
3 black pencil 0.56
4 yellow ashtray 2.75
重命名轴索引
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reindex = { 0: ‘first‘, 1: ‘second‘, 2: ‘third‘, 3: ‘fourth‘, 4: ‘fifth‘}temp = frame.rename(reindex)print(temp)
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color item price
first white ball 5.56
second red mug 4.20
third green pen 1.30
fourth black pencil 0.56
fifth yellow ashtray 2.75
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recolumn = { ‘item‘:‘object‘, ‘price‘: ‘value‘}temp = frame.rename(index=reindex, columns=recolumn)print(temp)
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color object value
first white ball 5.56
second red mug 4.20
third green pen 1.30
fourth black pencil 0.56
fifth yellow ashtray 2.75
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temp = frame.rename(index={1:‘first‘}, columns={‘item‘:‘object‘})print(temp)
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color object price
0 white ball 5.56
first red mug 4.20
2 green pen 1.30
3 black pencil 0.56
4 yellow ashtray 2.75
6.4 离散化和面元划分 132
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results = [12,34,67,55,28,90,99,12,3,56,74,44,87,23,49,89,87]bins = [0,25,50,75,100]cat = pd.cut(results, bins)cat
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[(0, 25], (25, 50], (50, 75], (50, 75], (25, 50], ..., (75, 100], (0, 25], (25, 50], (75, 100], (75, 100]]
Length: 17
Categories (4, interval[int64]): [(0, 25] < (25, 50] < (50, 75] < (75, 100]]
D:\ProgramData\Anaconda3_32\lib\site-packages\ipykernel_launcher.py:1: FutureWarning: ‘labels‘ is deprecated. Use ‘codes‘ instead
"""Entry point for launching an IPython kernel.
array([0, 1, 2, 2, 1, 3, 3, 0, 0, 2, 2, 1, 3, 0, 1, 3, 3], dtype=int8)
(75, 100] 5
(50, 75] 4
(25, 50] 4
(0, 25] 4
dtype: int64
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bin_names = [‘unlikely‘,‘less likely‘,‘likely‘,‘highly likely‘]pd.cut(results, bins, labels=bin_names)
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[unlikely, less likely, likely, likely, less likely, ..., highly likely, unlikely, less likely, highly likely, highly likely]
Length: 17
Categories (4, object): [unlikely < less likely < likely < highly likely]
[(2.904, 22.2], (22.2, 41.4], (60.6, 79.8], (41.4, 60.6], (22.2, 41.4], ..., (79.8, 99.0], (22.2, 41.4], (41.4, 60.6], (79.8, 99.0], (79.8, 99.0]]
Length: 17
Categories (5, interval[float64]): [(2.904, 22.2] < (22.2, 41.4] < (41.4, 60.6] < (60.6, 79.8] < (79.8, 99.0]]
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quintiles = pd.qcut(results, 5)quintiles
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[(2.999, 24.0], (24.0, 46.0], (62.6, 87.0], (46.0, 62.6], (24.0, 46.0], ..., (62.6, 87.0], (2.999, 24.0], (46.0, 62.6], (87.0, 99.0], (62.6, 87.0]]
Length: 17
Categories (5, interval[float64]): [(2.999, 24.0] < (24.0, 46.0] < (46.0, 62.6] < (62.6, 87.0] < (87.0, 99.0]]
1
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pd.value_counts(quintiles)
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(62.6, 87.0] 4
(2.999, 24.0] 4
(87.0, 99.0] 3
(46.0, 62.6] 3
(24.0, 46.0] 3
dtype: int64
异常值检测和过滤
123
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randframe = pd.DataFrame(np.random.randn(1000,3))temp = randframe.describe()print(temp)
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0 1 2
count 1000.000000 1000.000000 1000.000000
mean -0.017081 0.009233 -0.016035
std 0.983899 0.986440 0.961825
min -3.834283 -3.725847 -2.810249
25% -0.651448 -0.645679 -0.674606
50% -0.031185 0.004074 -0.006893
75% 0.633531 0.721898 0.669395
max 3.006011 3.018671 3.290535
0 0.983899
1 0.986440
2 0.961825
dtype: float64
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temp = randframe[(np.abs(randframe) > (3*randframe.std())).any(1)]print(temp)
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0 1 2
66 -1.552807 1.813374 3.141080
169 -1.154864 -3.725847 -0.647544
226 -3.411732 1.907356 -0.004208
426 3.006011 0.554358 0.687883
457 -1.282513 -1.312958 3.290535
465 -3.834283 -0.310886 1.280224
748 2.977327 -0.937580 0.361383
764 -0.000591 3.018671 -1.180475
6.5 排序 136
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nframe = pd.DataFrame(np.arange(25).reshape(5,5))print(nframe)
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0 1 2 3 4
0 0 1 2 3 4
1 5 6 7 8 9
2 10 11 12 13 14
3 15 16 17 18 19
4 20 21 22 23 24
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new_order = np.random.permutation(5)print(new_order)
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[4 2 1 3 0]
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temp = nframe.take(new_order)print(temp)
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0 1 2 3 4
4 20 21 22 23 24
2 10 11 12 13 14
1 5 6 7 8 9
3 15 16 17 18 19
0 0 1 2 3 4
123
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new_order = [3,4,2]temp = nframe.take(new_order)print(temp)
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0 1 2 3 4
3 15 16 17 18 19
4 20 21 22 23 24
2 10 11 12 13 14
随机取样
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sample = np.random.randint(0, len(nframe), size=3)sample
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array([3, 3, 3])
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temp = nframe.take(sample)print(temp)
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0 1 2 3 4
3 15 16 17 18 19
3 15 16 17 18 19
3 15 16 17 18 19
6.6 字符串处理 137
6.6.1 内置的字符串处理方法 137
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text = ‘16 Bolton Avenue , Boston‘text.split(‘,‘)
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[‘16 Bolton Avenue ‘, ‘ Boston‘]
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tokens = [s.strip() for s in text.split(‘,‘)]tokens
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[‘16 Bolton Avenue‘, ‘Boston‘]
123
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address, city = [s.strip() for s in text.split(‘,‘)]print(address)print(city)
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16 Bolton Avenue
Boston
‘16 Bolton Avenue,Boston‘
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strings = [‘A+‘,‘A‘,‘A-‘,‘B‘,‘BB‘,‘BBB‘,‘C+‘]‘;‘.join(strings)
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‘A+;A;A-;B;BB;BBB;C+‘
True
19
19
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-113-e44f5210d36c> in <module>()
----> 1 text.index(‘New York‘)
ValueError: substring not found
2
1
1
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text.replace(‘Avenue‘,‘Street‘)
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‘16 Bolton Street , Boston‘
‘6 Bolton Avenue , Boston‘
6.6.2 正则表达式 139
123
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import retext = "This is an\t odd \n text!"re.split(‘\s+‘, text)
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[‘This‘, ‘is‘, ‘an‘, ‘odd‘, ‘text!‘]
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regex = re.compile(‘\s+‘)regex.split(text)
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[‘This‘, ‘is‘, ‘an‘, ‘odd‘, ‘text!‘]
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text = ‘This is my address: 16 Bolton Avenue, Boston‘re.findall(‘A\w+‘,text)
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[‘Avenue‘]
1
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re.findall(‘[A,a]\w+‘,text)
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[‘address‘, ‘Avenue‘]
1
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re.search(‘[A,a]\w+‘,text)
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<_sre.SRE_Match object; span=(11, 18), match=‘address‘>
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search = re.search(‘[A,a]\w+‘,text)search.start()
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11
18
1
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text[search.start():search.end()]
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‘address‘
1
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re.match(‘[A,a]\w+‘,text)
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<_sre.SRE_Match object; span=(0, 4), match=‘This‘>
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match = re.match(‘T\w+‘,text)text[match.start():match.end()]
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‘This‘
6.7 数据聚合 140
6.7.1 GroupBy 141
6.7.2 实例 141
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frame = pd.DataFrame({ ‘color‘: [‘white‘,‘red‘,‘green‘,‘red‘,‘green‘], ‘object‘: [‘pen‘,‘pencil‘,‘pencil‘,‘ashtray‘,‘pen‘], ‘price1‘ : [5.56,4.20,1.30,0.56,2.75], ‘price2‘ : [4.75,4.12,1.60,0.75,3.15]})print(frame)
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color object price1 price2
0 white pen 5.56 4.75
1 red pencil 4.20 4.12
2 green pencil 1.30 1.60
3 red ashtray 0.56 0.75
4 green pen 2.75 3.15
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group = frame[‘price1‘].groupby(frame[‘color‘])group
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<pandas.core.groupby.SeriesGroupBy object at 0x06923E30>
{‘green‘: Int64Index([2, 4], dtype=‘int64‘),
‘red‘: Int64Index([1, 3], dtype=‘int64‘),
‘white‘: Int64Index([0], dtype=‘int64‘)}
color
green 2.025
red 2.380
white 5.560
Name: price1, dtype: float64
color
green 4.05
red 4.76
white 5.56
Name: price1, dtype: float64
12
|
ggroup = frame[‘price1‘].groupby([frame[‘color‘],frame[‘object‘]])ggroup.groups
|
{(‘green‘, ‘pen‘): Int64Index([4], dtype=‘int64‘),
(‘green‘, ‘pencil‘): Int64Index([2], dtype=‘int64‘),
(‘red‘, ‘ashtray‘): Int64Index([3], dtype=‘int64‘),
(‘red‘, ‘pencil‘): Int64Index([1], dtype=‘int64‘),
(‘white‘, ‘pen‘): Int64Index([0], dtype=‘int64‘)}
color object
green pen 2.75
pencil 1.30
red ashtray 0.56
pencil 4.20
white pen 5.56
Name: price1, dtype: float64
6.7.3 等级分组 142
12
|
temp = frame[[‘price1‘,‘price2‘]].groupby(frame[‘color‘]).mean()print(temp)
|
price1 price2
color
green 2.025 2.375
red 2.380 2.435
white 5.560 4.750
12
|
temp = frame.groupby(frame[‘color‘]).mean()print(temp)
|
price1 price2
color
green 2.025 2.375
red 2.380 2.435
white 5.560 4.750
6.8 组迭代 143
123
|
for name, group in frame.groupby(‘color‘): print(name) print(group)
|
green
color object price1 price2
2 green pencil 1.30 1.60
4 green pen 2.75 3.15
red
color object price1 price2
1 red pencil 4.20 4.12
3 red ashtray 0.56 0.75
white
color object price1 price2
0 white pen 5.56 4.75
6.8.1 链式转换 144
12
|
result1 = frame[‘price1‘].groupby(frame[‘color‘]).mean()type(result1)
|
pandas.core.series.Series
12
|
result2 = frame.groupby(frame[‘color‘]).mean()type(result2)
|
pandas.core.frame.DataFrame
1
|
frame[‘price1‘].groupby(frame[‘color‘]).mean()
|
color
green 2.025
red 2.380
white 5.560
Name: price1, dtype: float64
1
|
frame.groupby(frame[‘color‘])[‘price1‘].mean()
|
color
green 2.025
red 2.380
white 5.560
Name: price1, dtype: float64
1
|
(frame.groupby(frame[‘color‘]).mean())[‘price1‘]
|
color
green 2.025
red 2.380
white 5.560
Name: price1, dtype: float64
12
|
means = frame.groupby(‘color‘).mean().add_prefix(‘mean_‘)print(means)
|
mean_price1 mean_price2
color
green 2.025 2.375
red 2.380 2.435
white 5.560 4.750
6.8.2 分组函数 145
12
|
group = frame.groupby(‘color‘)group[‘price1‘].quantile(0.6)
|
color
green 2.170
red 2.744
white 5.560
Name: price1, dtype: float64
12
|
def myrange(series): return series.max() - series.min()
|
1
|
group[‘price1‘].agg(myrange)
|
color
green 1.45
red 3.64
white 0.00
Name: price1, dtype: float64
12
|
temp = group.agg(myrange)print(temp)
|
price1 price2
color
green 1.45 1.55
red 3.64 3.37
white 0.00 0.00
12
|
temp = group[‘price1‘].agg([‘mean‘,‘std‘,myrange])print(temp)
|
mean std myrange
color
green 2.025 1.025305 1.45
red 2.380 2.573869 3.64
white 5.560 NaN 0.00
6.9 高级数据聚合 145
1234
|
frame = pd.DataFrame({ ‘color‘:[‘white‘,‘red‘,‘green‘,‘red‘,‘green‘], ‘price1‘:[5.56,4.20,1.30,0.56,2.75], ‘price2‘:[4.75,4.12,1.60,0.75,3.15]})print(frame)
|
color price1 price2
0 white 5.56 4.75
1 red 4.20 4.12
2 green 1.30 1.60
3 red 0.56 0.75
4 green 2.75 3.15
12
|
sums = frame.groupby(‘color‘).sum().add_prefix(‘tot_‘)print(sums)
|
tot_price1 tot_price2
color
green 4.05 4.75
red 4.76 4.87
white 5.56 4.75
12
|
temp = pd.merge(frame,sums,left_on=‘color‘,right_index=True)print(temp)
|
color price1 price2 tot_price1 tot_price2
0 white 5.56 4.75 5.56 4.75
1 red 4.20 4.12 4.76 4.87
3 red 0.56 0.75 4.76 4.87
2 green 1.30 1.60 4.05 4.75
4 green 2.75 3.15 4.05 4.75
12
|
temp = frame.groupby(‘color‘).transform(np.sum).add_prefix(‘tot_‘)print(temp)
|
tot_price1 tot_price2
0 5.56 4.75
1 4.76 4.87
2 4.05 4.75
3 4.76 4.87
4 4.05 4.75
12345
|
frame = pd.DataFrame( { ‘color‘:[‘white‘,‘black‘,‘white‘,‘white‘,‘black‘,‘black‘], ‘status‘:[‘up‘,‘up‘,‘down‘,‘down‘,‘down‘,‘up‘], ‘value1‘:[12.33,14.55,22.34,27.84,23.40,18.33], ‘value2‘:[11.23,31.80,29.99,31.18,18.25,22.44]})print(frame)
|
color status value1 value2
0 white up 12.33 11.23
1 black up 14.55 31.80
2 white down 22.34 29.99
3 white down 27.84 31.18
4 black down 23.40 18.25
5 black up 18.33 22.44
12
|
temp = frame.groupby([‘color‘,‘status‘]).apply( lambda x: x.max())print(temp)
|
color status value1 value2
color status
black down black down 23.40 18.25
up black up 18.33 31.80
white down white down 27.84 31.18
up white up 12.33 11.23
12
|
temp = frame.rename(index=reindex, columns=recolumn)print(temp)
|
color status value1 value2
first white up 12.33 11.23
second black up 14.55 31.80
third white down 22.34 29.99
fourth white down 27.84 31.18
fifth black down 23.40 18.25
5 black up 18.33 22.44
12
|
temp = pd.date_range(‘1/1/2015‘, periods=10, freq= ‘H‘)print(temp)
|
DatetimeIndex([‘2015-01-01 00:00:00‘, ‘2015-01-01 01:00:00‘,
‘2015-01-01 02:00:00‘, ‘2015-01-01 03:00:00‘,
‘2015-01-01 04:00:00‘, ‘2015-01-01 05:00:00‘,
‘2015-01-01 06:00:00‘, ‘2015-01-01 07:00:00‘,
‘2015-01-01 08:00:00‘, ‘2015-01-01 09:00:00‘],
dtype=‘datetime64[ns]‘, freq=‘H‘)
12
|
timeseries = pd.Series(np.random.rand(10), index=temp)timeseries
|
2015-01-01 00:00:00 0.463135
2015-01-01 01:00:00 0.170738
2015-01-01 02:00:00 0.542155
2015-01-01 03:00:00 0.536056
2015-01-01 04:00:00 0.606624
2015-01-01 05:00:00 0.011034
2015-01-01 06:00:00 0.277493
2015-01-01 07:00:00 0.301076
2015-01-01 08:00:00 0.170235
2015-01-01 09:00:00 0.165120
Freq: H, dtype: float64
123
|
timetable = pd.DataFrame( {‘date‘: temp, ‘value1‘ : np.random.rand(10), ‘value2‘ : np.random.rand(10)})print(timetable)
|
date value1 value2
0 2015-01-01 00:00:00 0.783525 0.025861
1 2015-01-01 01:00:00 0.829443 0.642484
2 2015-01-01 02:00:00 0.260990 0.350753
3 2015-01-01 03:00:00 0.699793 0.118472
4 2015-01-01 04:00:00 0.349411 0.228708
5 2015-01-01 05:00:00 0.382496 0.902575
6 2015-01-01 06:00:00 0.896227 0.934669
7 2015-01-01 07:00:00 0.829987 0.941199
8 2015-01-01 08:00:00 0.479027 0.203317
9 2015-01-01 09:00:00 0.132429 0.102593
12
|
timetable[‘cat‘] = [‘up‘,‘down‘,‘left‘,‘left‘,‘up‘,‘up‘,‘down‘,‘right‘,‘right‘,‘up‘]print(timetable)
|
date value1 value2 cat
0 2015-01-01 00:00:00 0.783525 0.025861 up
1 2015-01-01 01:00:00 0.829443 0.642484 down
2 2015-01-01 02:00:00 0.260990 0.350753 left
3 2015-01-01 03:00:00 0.699793 0.118472 left
4 2015-01-01 04:00:00 0.349411 0.228708 up
5 2015-01-01 05:00:00 0.382496 0.902575 up
6 2015-01-01 06:00:00 0.896227 0.934669 down
7 2015-01-01 07:00:00 0.829987 0.941199 right
8 2015-01-01 08:00:00 0.479027 0.203317 right
9 2015-01-01 09:00:00 0.132429 0.102593 up
6.10 小结 148
原文地址：https://www.cnblogs.com/LearnFromNow/p/9349929.html
时间： 2025-01-10 16:34:12
