Book Image

NumPy: Beginner's Guide

By : Ivan Idris
Book Image

NumPy: Beginner's Guide

By: Ivan Idris

Overview of this book

Table of Contents (21 chapters)
NumPy Beginner's Guide Third Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
NumPy Functions' References
Index

Time for action – determining eigenvalues and eigenvectors


Let's calculate the eigenvalues of a matrix:

  1. Create a matrix as shown in the following:

    A = np.mat("3 -2;1 0")
    print("A\n", A)

    The matrix we created looks like the following:

    A
    [[ 3 -2]
     [ 1  0]]
    
  2. Call the eigvals() function:

    print("Eigenvalues", np.linalg.eigvals(A))

    The eigenvalues of the matrix are as follows:

    Eigenvalues [ 2.  1.]
    
  3. Determine eigenvalues and eigenvectors with the eig() function. This function returns a tuple, where the first element contains eigenvalues and the second element contains corresponding eigenvectors, arranged column-wise:

    eigenvalues, eigenvectors = np.linalg.eig(A)
    print("First tuple of eig", eigenvalues)
    print("Second tuple of eig\n", eigenvectors)

    The eigenvalues and eigenvectors appear as follows:

    First tuple of eig [ 2.  1.]
    Second tuple of eig
    [[ 0.89442719  0.70710678]
     [ 0.4472136   0.70710678]]
    
  4. Check the result with the dot() function by calculating the right and left side of the eigenvalues equation...