Let's experiment with different ways to access individual elements and parts of a matrix. Enter and evaluate the following code:
A = Matrix(QQ, [[0, -1, -1, 1], [1, 1, 1, 1], [2, 4, 1, -2],
[3, 1, -2, 2]])
print("Matrix A:")
show(A)
# Getting elements of a matrix
print("A[0] = {0}".format(A[0]))
print("A[1, 2] = {0}".format(A[1, 2]))
print("A[2, 1] = {0}".format(A[2, 1]))
print("A[0:2]")
show(A[0:2])
print("A[0, 2:4] = {0}".format(A[0, 2:4]))
print("A[:,0]:")
show(A[:,0])
# Getting parts of a matrix
print("Third row:")
print(A.row(2))
print("Second column:")
print(A.column(1))
print("Lower right submatrix:")
show(A.submatrix(2, 2, 2, 2))The result should look like this:
