July 2017
Intermediate to advanced
796 pages
18h 55m
English
Content preview from Scala and Spark for Big Data Analytics
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Window functions
Window functions allow you to perform aggregations over a window of data rather than entire data or some filtered data. The use cases of such window functions are:
- Cumulative sum
- Delta from previous value for same key
- Weighted moving average
The best way to understand window functions is to imagine a sliding window over the larger dataset universe. You can specify a window looking at three rows T-1, T, and T+1, and by performing a simple calculation. You can also specify a window of latest/most recent ten values:
The API for the window specification requires three properties, the partitionBy(), orderBy(), and the rowsBetween() ...
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