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Ch. 11 Summarization (11.2 Crosstab (Useful for transforming "…
Ch. 11 Summarization
11.2 Crosstab
Uses content inside columns to create new columns
Useful for transforming "skinny" data
transform rows to columns
Ex: expanding "DrinkType" to "Coffee" "Tea" and "Energy Drink" Use numbers instead of string names
Skinny data
Each "event" stored in its own row
common data shape
Easier to apply summarization functions
11.1 Summarize
One or more columns of data selected to create a "bucket" for each group
Ex: Summarize by EmployeeId. Every employee's row placed inside bucket. Can count how many rows using Count function
Can summarize by more than one column
Ex: using EmployeeId and OrderDate
Common functions
count
sum
min
max
first
last
average
median
mode
standard deviation