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15 Math Concepts Every Data Scientist Should Know

You're reading from   15 Math Concepts Every Data Scientist Should Know Understand and learn how to apply the math behind data science algorithms

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Product type Paperback
Published in Aug 2024
Publisher Packt
ISBN-13 9781837634187
Length 510 pages
Edition 1st Edition
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Author (1):
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David Hoyle David Hoyle
Author Profile Icon David Hoyle
David Hoyle
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Table of Contents (21) Chapters Close

Preface 1. Part 1: Essential Concepts FREE CHAPTER
2. Chapter 1: Recap of Mathematical Notation and Terminology 3. Chapter 2: Random Variables and Probability Distributions 4. Chapter 3: Matrices and Linear Algebra 5. Chapter 4: Loss Functions and Optimization 6. Chapter 5: Probabilistic Modeling 7. Part 2: Intermediate Concepts
8. Chapter 6: Time Series and Forecasting 9. Chapter 7: Hypothesis Testing 10. Chapter 8: Model Complexity 11. Chapter 9: Function Decomposition 12. Chapter 10: Network Analysis 13. Part 3: Selected Advanced Concepts
14. Chapter 11: Dynamical Systems 15. Chapter 12: Kernel Methods 16. Chapter 13: Information Theory 17. Chapter 14: Non-Parametric Bayesian Methods 18. Chapter 15: Random Matrices 19. Index 20. Other Books You May Enjoy

Exercises

The following is a series of exercises. Answers to all the exercises are given in the Answers_to_Exercises_Chap14.ipynb Jupyter Notebook in the GitHub repository:

  1. The Matérn kernel function, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>k</mml:mi><mml:mfenced separators="|"><mml:mrow><mml:munder underaccent="false"><mml:mrow><mml:mi>x</mml:mi></mml:mrow><mml:mo>_</mml:mo></mml:munder><mml:mo>,</mml:mo><mml:munder underaccent="false"><mml:mrow><mml:mi>y</mml:mi></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:mrow></mml:mfenced></mml:math>, can be thought of as a generalization of the RBF kernel. It is of the following form:

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow><mrow><mi>k</mi><mfenced open="(" close=")"><mrow><munder><mi>x</mi><mo stretchy="true">_</mo></munder><mo>,</mo><munder><mi>y</mi><mo stretchy="true">_</mo></munder></mrow></mfenced><mo>=</mo><mfrac><mn>1</mn><mrow><mi mathvariant="normal">Γ</mi><mfenced open="(" close=")"><mi>ν</mi></mfenced><msup><mn>2</mn><mrow><mi mathvariant="normal">ν</mi><mo>−</mo><mn>1</mn></mrow></msup></mrow></mfrac><msup><mfenced open="(" close=")"><mrow><mfrac><msqrt><mrow><mn>2</mn><mi>ν</mi></mrow></msqrt><mi>b</mi></mfrac><mo>|</mo><munder><mi>x</mi><mo stretchy="true">_</mo></munder><mo>−</mo><munder><mi>y</mi><mo stretchy="true">_</mo></munder><mo>|</mo></mrow></mfenced><mi mathvariant="normal">ν</mi></msup><msub><mi>K</mi><mi mathvariant="normal">ν</mi></msub><mfenced open="(" close=")"><mrow><mfrac><msqrt><mrow><mn>2</mn><mi>ν</mi></mrow></msqrt><mi mathvariant="normal">b</mi></mfrac><mo>|</mo><munder><mi>x</mi><mo stretchy="true">_</mo></munder><mo>−</mo><munder><mi>y</mi><mo stretchy="true">_</mo></munder><mo>|</mo></mrow></mfenced></mrow></mrow></math>

Eq. 29

<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:msub><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mi>ν</mml:mi></mml:mrow></mml:msub><mml:mfenced separators="|"><mml:mrow><mml:mi>z</mml:mi></mml:mrow></mml:mfenced></mml:math> is the modified Bessel function of the second kind. The Matérn kernel is specified by the parameters, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>ν</mml:mi></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>b</mml:mi></mml:math>. The lengthscale parameter, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>b</mml:mi></mml:math>, plays a similar role to the length-scale parameter, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>b</mml:mi></mml:math>, in the RBF kernel in Eq. 10. The parameter, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>ν</mml:mi></mml:math>, controls how smooth the functions are when we use a GP prior with a Matérn covariance kernel.

Using the data from the code example in the main text and a Matérn kernel with the default value, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>ν</mml:mi><mml:mo>=</mml:mo><mml:mn>1.5</mml:mn></mml:math>, fit a GPR model to the data. Make predictions for a range of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>x</mml:mi></mml:math> values. Note that for the Matérn kernel, the parameter, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>ν</mml:mi></mml:math>, is not optimized by the scikit-learn fitting process, so if you instantiate a Matérn kernel...

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