Time for action – creating a matrix from other matrices

We will create a matrix from two smaller matrices, as follows:

1. First create a two-by-two identity matrix:

   A = np.eye(2)
   print "A", A

   The identity matrix looks like this:

   A [[ 1.  0.]
    [ 0.  1.]]
   

   Create another matrix like A and multiply by 2:

   B = 2 * A
   print "B", B

   The second matrix is as follows:

   B [[ 2.  0.]
    [ 0.  2.]]
   

2. Create the compound matrix from a string. The string uses the same format as the mat function; only, you can use matrices instead of numbers.

   print "Compound matrix\n", np.bmat("A B; A B")

   The compound matrix is shown as follows:

   Compound matrix
   [[ 1.  0.  2.  0.]
    [ 0.  1.  0.  2.]
    [ 1.  0.  2.  0.]
    [ 0.  1.  0.  2.]]
   

What just happened?

We created a block matrix from two smaller matrices, with the bmat function. We gave the function a string containing the names of matrices instead of numbers (see bmatcreation.py):

import numpy as np

A = np.eye(2)
print "A", A
B = 2 * A
print "B", B
print "Compound matrix\n", np.bmat...