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
About the Author
About the Reviewers
NumPy Functions' References

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:

    [[ 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...