4.4.2 Altering an array using slices

You may alter an array using slices or by direct access. The following changes only one element in a  matrix :

M[1, 2] = 2.0 # scalar

Also, we may change one full row of the matrix:

M[2, :] = [1., 2., 3.] # vector

Similarly, we may also replace a full submatrix:

M[1:3, :] = array([[1., 2., 3.],[-1.,-2., -3.]])

There is a distinction between a column matrix and a vector. The following assignment with a column matrix returns no error: 

M[1:4, 1:2] = array([[1.],[0.],[-1.0]]) 

while the assignment with a vector returns a ValueError:

M[1:4, 1:2] = array([1., 0., -1.0]) #  error

The general slicing rules are shown in Table 4.3. The matrices and vectors in the preceding examples must have the right size to fit into matrix . You may also make use of the broadcasting rules (see Section 5.5: Broadcasting) to determine the allowed size of the replacement arrays. If the replacement array does not have...