Book Image

NumPy Essentials

By : Leo (Liang-Huan) Chin, Tanmay Dutta, Shane Holloway
Book Image

NumPy Essentials

By: Leo (Liang-Huan) Chin, Tanmay Dutta, Shane Holloway

Overview of this book

In today’s world of science and technology, it’s all about speed and flexibility. When it comes to scientific computing, NumPy tops the list. NumPy gives you both the speed and high productivity you need. This book will walk you through NumPy using clear, step-by-step examples and just the right amount of theory. We will guide you through wider applications of NumPy in scientific computing and will then focus on the fundamentals of NumPy, including array objects, functions, and matrices, each of them explained with practical examples. You will then learn about different NumPy modules while performing mathematical operations such as calculating the Fourier Transform; solving linear systems of equations, interpolation, extrapolation, regression, and curve fitting; and evaluating integrals and derivatives. We will also introduce you to using Cython with NumPy arrays and writing extension modules for NumPy code using the C API. This book will give you exposure to the vast NumPy library and help you build efficient, high-speed programs using a wide range of mathematical features.
Table of Contents (16 chapters)
NumPy Essentials
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface

Decomposition


There are there decompositions provided by numpy.linalg and in this section, we will cover two that are the most commonly used: singular value decomposition (svd) and QR factorization. Let's start by computing the eigenvalues and eigenvectors first. Before we get started, if you are not familiar with eigenvalues and eigenvectors, you may review them at https://en.wikipedia.org/wiki/Eigenvalues_and_eigenvectors. Let's start:

In [41]: x = np.random.randint(0, 10, 9).reshape(3,3) 
In [42]: x 
Out[42]: 
array([[ 1,  5,  0] 
       [ 7,  4,  0] 
       [ 2,  9,  8]]) 
In [42]: w, v = np.linalg.eig(x) 
In [43]: w 
Out[43]: array([ 8.,  8.6033,  -3.6033]) 
In [44]: v 
Out[44]: 
array([[ 0.,  0.0384,  0.6834] 
       [ 0.,  0.0583, -0.6292] 
       [ 1.,  0.9976,  0.3702]] 
) 

In the previous example, first we created a 3 x 3 ndarray using numpy.random.randint () and we computed the eigenvalues and eigenvectors...