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Chapter 11: Summarization (11.1 (aka group or group by (essentially…
Chapter 11: Summarization
when data is available that does not focus directly on the right unit
it must be aggregated or summarized
for example
customer calling support five times won't appear in customer data
it'll appear in customer support table
after joining, you'll see how many times they call customer support line
summarization reduces both the number of columns and the number of rows
11.1
aka group or group by
essentially creating a "bucket" for each unique group
example
employeeID for nine unique employees
possible to summarize by more than one column
functions that can be applied to data inside each bucket
count,sum,min,max,first,last,average, median, mode, standard deviation
11.2 Crosstab
uses the content inside columns to create new columns
transform what is currently listed in rows to column form
Free Drink Example (at the startup)
turn drink type into columns themselves
tea, coffee, and energy drink all become columns
then applying the count function
see how often each employee chose each drink