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Data Science with SQL Server Quick Start Guide

You're reading from   Data Science with SQL Server Quick Start Guide Integrate SQL Server with data science

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Product type Paperback
Published in Aug 2018
Publisher Packt
ISBN-13 9781789537123
Length 206 pages
Edition 1st Edition
Languages
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Author (1):
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Dejan Sarka Dejan Sarka
Author Profile Icon Dejan Sarka
Dejan Sarka
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Table of Contents (10) Chapters Close

Preface 1. Writing Queries with T-SQL FREE CHAPTER 2. Introducing R 3. Getting Familiar with Python 4. Data Overview 5. Data Preparation 6. Intermediate Statistics and Graphs 7. Unsupervised Machine Learning 8. Supervised Machine Learning 9. Other Books You May Enjoy

The entropy of a discrete variable

In the Information Theory, as defined by Claude E Shannon, information is a surprise. Surprise comes from diversity, not from equality. Considering the data, a variable that can occupy a single value only, actually a constant, has no surprise and no information.

Whatever case you take randomly from the dataset, you know the value of this variable in advance, and you are never surprised. To have at least some information in it, a variable must be at least dichotomous, meaning it must have a pool of at least two distinct values. Now, imagine that you take a case randomly out of the dataset, but you know the overall distribution of that variable. If one state is more frequent, appearing in 80% of cases, you would expect that state, of course. You would be surprised 20% of the time. With 50%—50% distribution, no matter which state you...

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