# CSNB143 – Discrete Structure - PowerPoint PPT Presentation

1 / 19

CSNB143 – Discrete Structure. MATRIX. MATRIX. Learning Outcomes Students should be able to read matrix and its entries without difficulties. Students should understand all matrices operations. Students should be able to differentiate different matrices and operations by different matrix.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

CSNB143 – Discrete Structure

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

## CSNB143 – Discrete Structure

MATRIX

### MATRIX

Learning Outcomes

• Students should be able to read matrix and its entries without difficulties.

• Students should understand all matrices operations.

• Students should be able to differentiate different matrices and operations by different matrix.

• Students should be able to identify Boolean matrices and how to operate them.

### MATRIX

Introduction

• An array of numbers arranged in m horizontal rows and n vertical columns:

• Ex 1:

A = a11a12…….a1n

a21a22…….a2n

......

......

......

am1am2…….amn

• The ith row of A is [ai1, ai2, ai3, …ain]; 1 im

• The jth column of A is a1j

a2j ; 1 jn

a3j

.

.amj

### MATRIX

Diagonal matrix

• We say that A is a matrix m x n. If m = n, then A is a square matrix of order n, and a11, a22, a33, ..ann form the main diagonal of A.

• aij which is in the ith row andjth column, is said to be the i,jth element of A or the (i, j) entry of A, often written as A = [aij].

• A square matrix A = [aij], for which every entry off the main diagonal is zero, that is aij = 0 for i j, is called a diagonal matrix.

• Ex 2:

A = 8 0 0 0

0 3 0 0

0 0 7 0

0 0 0 1

### MATRIX

• Two m x n matrices A and B, A = [aij] and B = [bij], are said to be equal if aij = bij for 1 im, 1 jn; that is, if corresponding elements are the same.

• Ex 3:

A = a 5 3B = 1 5 x

2 7 -1y 7 -1

3 b 03 4 0

• So, if A = B, then a = 1, x = 3, y = 2, b = 4.

### MATRIX

Matrices Summation

• If A = [aij] and B = [bij] are m x n matrices, then the sum of A and B is matrix C = [cij], defined by

cij = aij + bij; 1 im, 1 j n.

• C is obtained by adding the corresponding elements of A and B.

• Ex 4:

A = 1 5 3B = 2 0 3C = 3 5 6

2 7 -1 +6 1 3 =8 8 23 4 0-3 1 90 5 9

• The sum of the matrices A and B is defined only when A and B have the same number of rows and the same number of columns (same dimension).

### MATRIX

Exercise 1:

a) Identify which matrices that the summation process can be done.

b) Compute C + G, A + D, E + H, A + F.

A = 2 1 B = 2 1 3C = 7 2D = 3 3

4 84 5 74 22 5

1 5

E = 2 -3 7F = -2 -1G = 4 3H = 1 2 3

0 4 7 -4 -85 14 5 6

3 1 2-1 07 8 9

### MATRIX

A matrix in when all of its entries are zero is called zero matrix, denoted by 0.

• Theorems involved in summation :

• A + B = B + A.

• (A + B) + C = A + (B + C).

• A + 0 = 0 + A = A.

Matrices Product

• If A = [aij] is an m x p matrix and B = [bij] is a p x n matrix, then the product of A and B, denoted AB, will produce the m x n matrix C = [cij], defined by

cij = ai1b1j + ai2b2j + … + aipbpj; 1 in, 1 j m

• That is, elements ai1, ai2, .. aip from ith row of A and elements b1j, b2j, .. bpj from jth column of B, are multiplied for each corresponding entries and add all the products.

### MATRIX

Ex 5:

A = 2 3 -4B = 3 1

1 2 3-2 2

2 x 3 5 -3

3 x 2

AB = 2(3) + 3(-2) + -4(5)2(1) + 3(2) + -4(-3)

1(3) + 2(-2) + 3(5)1(1) + 2(2) + 3(-3)

= 6 – 6 – 202 + 6 + 12

3 – 4 + 151 + 4 – 9

= -2020

14-4 2 x 2

Exercise 2:

a) Identify which matrices that the product process can be done. List all pairs.

b) Compute CA, AD, EG, BE, HE.

### MATRIX

• If A is an m x p matrix and B is a p x n matrix, in which AB will produce m x n, BA might be produce or not depends on:

• nm, then BA cannot be produced.

• n = m, pm @ n, then we can get BA but the size will be different from AB.

• n = m= p, A  B, then we can get BA, the size of BA and AB is the same, but AB  BA.

• n = m = p, A = B, then we can get BA, the size of BA and AB is the same, and AB = BA.

A B AB B ABA

(m x p) (p x n) (m x n) (p x n) (m x p) ?

2 x 3 3 x 4 2 x 4 3 x 4 2 x 3 X

2 x 3 3 x 2 2 x 2 3 X 2 2 X 33 X 3

2 X 2 2 X 2 2 X 2 2 X 2 2 X 22 X 2

2 1 3 19 5 3 1 2 1 8 6

2 3 3 3 15 11 3 3 2 312 12

### MATRIX

Identity matrix

• Let say A is a diagonal matrix n x n. If all entries on its diagonal are 1, it is called identity matrix, ordered n, written as I.

• Ex 7:

1 01 0 01 0 0 0

0 10 1 00 1 0 0

0 0 00 0 1 0

0 0 0 1

• Theorems involved are:

• A(BC) = (AB)C.

• A(B + C) = AB + AC.

• (A + B)C = AC + BC.

• IA = AI = A.

### MATRIX

Transposition Matrix

• If A = [aij] is an m x n matrix, then AT = [aij]T is a n x m matrix, where

aijT= aji; 1 im, 1 jn

• It is called transposition matrix for A.

• Ex 8:

A = 2 -3 5AT = 2 6

6 1 3-3 1

5 3

• Theorems involved are:

• (AT)T = A

• (A + B)T = AT + BT

• (AB)T = BTAT

### MATRIX

• Matrix A = [aij] is said to be symmetric if AT = A, that is aij = aji,

• A is said to be symmetric if all entries are symmetrical to its main diagonal.

• Ex 9:

A = 12 -3B = 1 2 -3

2452 4 0

-3563 2 1

Symmetric Not Symmetric, why?

### MATRIX

Boolean Matrix and Its Operations

• Boolean matrix is an m x n matrix where all of its entries are either 1 or 0 only.

• There are three operations on Boolean:

• Join by

Given A = [aij] and B = [bij] are Boolean matrices with the same dimension, join by A and B, written as A  B, will produce a matrix C = [cij], where

cij = 1if aij = 1 OR bij = 1

0if aij = 0 AND bij = 0

• Meet

Meetfor A and B, both with the same dimension, written as A  B, will produce matrix D = [dij] where

dij= 1if aij = 1 AND bij = 1

0 if aij = 0 OR bij = 0

### MATRIX

• Ex 10: A = 1 0 1B = 1 1 0

• 0 1 10 0 1

• 1 1 00 1 0

• 0 1 01 1 0

• A  B = 1 1 1A  B = 1 0 0

• 0 1 10 0 1

• 1 1 00 1 0

• 1 1 00 1 0

### MATRIX

• Boolean product

• If A = [aij] is an m x p Boolean matrix, and B = [bij] is a p x n Boolean matrix, we can get a Boolean product for A and B written as A ⊙ B, producing C, where:

• cij = 1 if aik = 1 AND bkj = 1; 1 kp.

0other than that

• It is using the same way as normal matrix product.

### MATRIX

• Ex 11:

• A = 1 0 0 0B = 1 1 0

• 0 1 1 00 1 0

• 1 0 1 11 1 0

• 3 x 40 0 1

4 x 3

A ⊙ B = 1 + 0 + 0 + 01 + 0 + 0 + 00 + 0 + 0 + 0

0 + 0 + 1 + 00 + 1 + 1 + 00 + 0 + 0 + 0

1 + 0 + 1 + 01 + 0 + 1 + 00 + 0 + 0 + 1

• A ⊙ B = 1 1 0

1 1 0

1 1 1

3 x 3

### MATRIX

• Exercise 3:

• A = 1 0 0 0B = 0 1 0 0C = 0 0 1 0

0 1 1 00 0 1 11 0 0 0

0 0 0 10 1 0 11 1 0 0

1 1 0 00 0 1 01 1 1 0

• Find:

• A  B

• A  B

• A ⊙ B

• A  C

• A C

• A ⊙ C

• B  C

• B  C

• B ⊙ C