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Chapter 9 Data Integration (Union=Access more observations (For a proper…
Chapter 9 Data Integration
Join= Access more features
after a join, one or more new rows are created.
Table
any rectangular matrix containing data in column form
Left Outer Join
same as inner join but adds rows from the left table. that have no corresponding rows in the right table.
Inner Join
each row in the left table is combined horizontally.
Produces heaver row and two data rows.
Most common. Pair with left outer to handle 99% of what we need.
Right Outer Join
Same as inner but adds any rows from the right table.
header row and three data rows
Full outer
inner plus left&right outer join.
Header row and four data rows.
Combines two data sets with a shared identity value.
Union=Access more observations
For a proper machine learning environment, we have to integrate all data.
Allow us to combine two data sets.
When information is missing, it can be a best practice to average all relevant information instead of having a "null" value.
based on the assumption that there are multiple columns in common between A and C.