Gram-Schmidt Orthogonalization
Process and Orthonormalization
Numerical Linear Algebra
Isaac Amornortey Yowetu
NIMS-GHANA
September 22, 2020
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Outline
1 Orthogonalization Vrs Orthonormalization
2 Gram-Schmidt Process
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Orthogonalization Vrs
Orthonormalization
Orthogonalization
It is a process of constructing a set of orthogonal vectors
that span a particular subspace.
Suppose we have a set of linearly independent set of
vectors {v1, v2, ..., vn} ∈ V in the inner product space,
we can construct a set of orthogonal bases vectors
{u1, u2, ..., un} from the Inner Product or Euclidean space
that will be of the same subspace such that:
• the new set of vectors and the old set of vectors
must have the same linear span.
• every vector in the new set is orthogonal to every
other vector in the new set.
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Orthonormalization
It is a form of orthogonalization in which each resulting
vector is a unit vector.
Supppose {u1, u2, ..., un} as the orthogonal basis, then
w1 =
u1
||u1||
, w2 =
u2
||u2||
, ..., wn =
un
||un||
of which {w1, w2, ..., wn} be the orthonormal basis.
some Orthogonalization Algorithms
• Gram-Schmidt Process
• Householder Transformation
• Givens Rotation
Theorem
Any orthogonal set is linearly independent.
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Gram-Schmidt Process
Many Vectors
Considering a vector space V in an inner product space.
And {v1, v2, ...vn} be a basis for V, then:
u1 = v1 (1)
u2 = v2 −
< u1, v2 >
< u1, u1 >
u1 (2)
u3 = v3 −
< u1, v3 >
< u1, u1 >
u1 −
< u2, v3 >
< u2, u2 >
u2 (3)
... = · · · · · · · · · · · · · · · (4)
un = vn −
< u1, vn >
< u1, u1 >
u1−, ..., −
< un−1, vn >
< un−1, un−1 >
un−1
(5)
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Gram-Schmidt Process
Solved Problems
Example 1
Apply Gram-Schmidt orthogonalization process to the
sequence of vectors in R3
, and hence, find the
orthonormal basis.
v1 =


1
1
1

 , v2 =


1
2
0

 , v3 =


2
0
1


Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Solution
u1 = v1 =


1
1
1


u2 = v2 − proju1 (v2) =


1
2
0

 −
3
3


1
1
1

 =


0
1
−1


u3 = v3 − proju1 (v3) − proju2 (v3)
=


2
0
1

 −
3
3


1
1
1

 +
1
2


0
1
−1

 =


1
−0.5
−0.5


Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Finding the orthonormal basis
w1 =
u1
||u1||
=
1
√
3


1
1
1

 =


0.577
0.577
0.577


w2 =
u2
||u2||
=
1
√
2


0
1
−1

 =


0
0.707
−0.707


w3 =
u3
||u3||
=
√
6
2


0
0.5
−0.5

 =


0
0.4082
−0.4082


Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Example 2
Given that V is a subspace of R4
with basis




1
0
1
1



 ,




0
1
1
1




Find the orthogonal basis and their respective
orthonormal basis of V.
Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Solution
u1 = v1 =




1
0
1
1




u2 = v2 − proju1 v2 =




0
1
1
1



 −
2
3




1
0
1
1



 =




−2
3
0
1
3
1
3




Gram-Schmidt
Orthogonaliza-
tion Process and
Orthonormaliza-
tion
Isaac
Amornortey
Yowetu
Orthogonalization
Vrs Orthonor-
malization
Gram-Schmidt
Process
Finding the orthonormal basis
w1 =
u1
||u1||
=
1
√
3




1
0
1
1



 =




0.577
0
0.577
0.577




w2 =
u2
||u2||
=
√
6
3




−2
3
0
1
3
1
3



 =




−0.816
0
0.408
0.408





Gram schmidt orthogonalization | Orthonormal Process