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Pandas Basics 5
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Pandas BasicsLecture1.1
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Pandas DataFramesLecture1.2
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ApplyLecture1.3
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Boolean IndexingLecture1.4
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Null ValuesLecture1.5
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Data Transformations 6
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Log TransformationLecture2.1
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ClipLecture2.2
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StackLecture2.3
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Multi-IndexLecture2.4
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PivotLecture2.5
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Window FunctionsLecture2.6
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Statistics 4
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IntroductionLecture3.1
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Descriptive StatisticsLecture3.2
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Bollinger BandsLecture3.3
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Bollinger Bands Part 2Lecture3.4
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Reading and Writing Data 3
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Reading and Writing DataLecture4.1
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Using osLecture4.2
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Reading in ChunksLecture4.3
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Joins 5
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IntroductionLecture5.1
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JoinsLecture5.2
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Joining with DuplicatesLecture5.3
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Multi-index JoinsLecture5.4
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Column CollisionsLecture5.5
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Grouping 4
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IntroductionLecture6.1
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Combining Groupby and JoinLecture6.2
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Multi-index GroupingLecture6.3
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Grouping and ApplyLecture6.4
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Introduction to Numpy 4
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IntroductionLecture7.1
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Extending to 2 DimensionsLecture7.2
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Extending to 3 DimensionsLecture7.3
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ReshapingLecture7.4
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Randomness 2
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Random SeedLecture8.1
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Random FunctionsLecture8.2
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Numpy Data Functionality 1
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Numpy Data FunctionalityLecture9.1
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Stack
Stack¶
The stack function takes a dataframe and brings down each column. It can be tough to explain it so let’s just see what it looks like.
In [9]:
#Create the GDP object
gdp = pd.DataFrame([[.03, .04, .03],
[.05, .03, .01],
[.02, .02, .07],
[.03, .01, .02]], index=["Q1", "Q2", "Q3", "Q4"], columns=['Country A', "Country B", "Country C"])
print("Before stack:")
print(gdp)
print()
#Stack
gdp = gdp.stack()
print("After stack:")
print(gdp)
Before stack:
Country A Country B Country C
Q1 0.03 0.04 0.03
Q2 0.05 0.03 0.01
Q3 0.02 0.02 0.07
Q4 0.03 0.01 0.02
After stack:
Q1 Country A 0.03
Country B 0.04
Country C 0.03
Q2 Country A 0.05
Country B 0.03
Country C 0.01
Q3 Country A 0.02
Country B 0.02
Country C 0.07
Q4 Country A 0.03
Country B 0.01
Country C 0.02
dtype: float64
So you will see that we went from 4x3 dataframe to 12 values. One result of using this is that we now have a new type of index. Let's check out what we get out.
In [10]:
#Print out the GDP index after stacking
print(gdp.index)
MultiIndex([('Q1', 'Country A'),
('Q1', 'Country B'),
('Q1', 'Country C'),
('Q2', 'Country A'),
('Q2', 'Country B'),
('Q2', 'Country C'),
('Q3', 'Country A'),
('Q3', 'Country B'),
('Q3', 'Country C'),
('Q4', 'Country A'),
('Q4', 'Country B'),
('Q4', 'Country C')],
)
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