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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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Toc

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_Chap15.ipynb Jupyter notebook in the GitHub repository.

  1. Create a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mn>2000</mml:mn><mml:mo>×</mml:mo><mml:mn>2000</mml:mn></mml:math> symmetric matrix <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:munder underaccent="false"><mml:mrow><mml:munder underaccent="false"><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:math> using the following relationship:

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow><mrow><munder><munder><mi>M</mi><mo stretchy="true">_</mo></munder><mo stretchy="true">_</mo></munder><mo>=</mo><mfrac><mn>1</mn><mn>2</mn></mfrac><mfenced open="(" close=")"><mrow><munder><munder><mi>A</mi><mo stretchy="true">_</mo></munder><mo stretchy="true">_</mo></munder><mo>+</mo><msup><munder><munder><mi>A</mi><mo stretchy="true">_</mo></munder><mo stretchy="true">_</mo></munder><mi mathvariant="normal">⊤</mi></msup></mrow></mfenced></mrow></mrow></math>

Eq.13

The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:munder underaccent="false"><mml:mrow><mml:munder underaccent="false"><mml:mrow><mml:mi>A</mml:mi></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:math> matrix should have its matrix elements drawn from the standard normal distribution with a probability of 0.5, and from the mean-zero unit-variance Laplace distribution in Eq.4, with a probability of 0.5. Calculate the eigenvalues, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>λ</mml:mi></mml:math>, of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:munder underaccent="false"><mml:mrow><mml:munder underaccent="false"><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:mrow><mml:mo>_</mml:mo></mml:munder></mml:math> and compute the empirical density of scaled eigenvalues <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mrow><mml:mrow><mml:mi>λ</mml:mi></mml:mrow><mml:mo>/</mml:mo><mml:mrow><mml:msqrt><mml:mi>N</mml:mi></mml:msqrt></mml:mrow></mml:mrow></mml:math>. Compare this empirical density to the semicircle law in Eq.2.

Tip

You can draw a value <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> from the mean-zero unit-variance Laplace distribution by first drawing a value <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mi>u</mml:mi></mml:math> from the uniform distribution, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mrow><mi mathvariant="normal">u</mi><mtext>niform</mtext><mfenced open="(" close=")"><mrow><mo>−</mo><mn>0.5</mn><mo>,</mo><mn>0.5</mn></mrow></mfenced></mrow></mrow></math>, then calculating <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> as follows:

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><mrow><mrow><mi>x</mi><mo>=</mo><mo>−</mo><mfrac><mn>1</mn><msqrt><mn>2</mn></msqrt></mfrac><mtext>sign</mtext><mfenced open="(" close=")"><mi>u</mi></mfenced><mi>ln</mi><mfenced open="(" close=")"><mrow><mn>1</mn><mo>−</mo><mn>2</mn><mfenced open="|" close="|"><mi>u</mi></mfenced></mrow></mfenced></mrow></mrow></math>

Eq.14

Alternatively, you can use the numpy.random.laplace NumPy function to sample the values directly.

2. From the definition of the GUE in Eq.7, generate a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math"><mml:mn>2000</mml:mn><mml:mo>×</mml:mo><mml:mn>2000</mml:mn></mml:math> GUE matrix and compute its...

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