Constructing a Simple Matrix

Constructing a Simple Matrix

A = [row1; row2; ...; rown]

Ex: A = [12 62 93 -8 22; 16 2 87 43 91; -4 17 -72 95 6]

A =

12 62 93 -8 22

16 2 87 43 91

-4 17 -72 95 6

Creating a Magic Square Matrix

Ex: A = magic(4)

A =

16 2 3 13

5 11 10 8

9 7 6 12

4 14 15 1

Creating a Random Matrix

Ex: A = rand(3) * 20

A =

3.8686 10.8335 7.5675

13.6445 3.0175 17.2002

6.0553 13.9580 17.0731

Concatenating Matrices

Ex: A = ones(2, 5) * 6; B = rand(3, 5);

C = [A; B] ;

Replicating a Matrix

repmat(M, v, h)

Ex: A = [8 1 6; 3 5 7; 4 9 2];

B = repmat(A,1,2)

B =

8 1 6 8 1 6

3 5 7 3 5 7

4 9 2 4 9 2

Combining Single and Double Types

Ex: x = [single(4.5) single(-2.8) pi 5.73*10^300]

x =

4.5000 -2.8000 3.1416 Inf

class(x) % Display the data type of x

ans =

single

Combining Integer and Double Types

Ex: x = [int8(21) int8(-22) int8(23) pi 45/6]

x =

21 -22 23 3 7

class(x)

ans =

int8

Combining Character and Double Types

Ex: x = ['A' 'B' 'C' 68 69 70]

x =

ABCDEF

class(x)

ans =

char

Combining Logical and Double Types

Ex: x = [true false false pi sqrt(7)]

x =

1.0000 0 0 3.1416 2.6458

class(x)

ans =

double

Accessing Single Elements

For example, for a 3-by-3 magic square A

A =

8 1 6

3 5 7

4 9 2

you would access the element at row 3, column 2 with A(3, 2)

ans =

9

Linear Indexing

Ex: A = [2 6 9; 4 2 8; 3 0 1]

A = 2 6 9

4 2 8

3 5 1

is actually stored in memory as the sequence 2, 4, 3, 6, 2, 5, 9, 8, 1

Functions That Control Indexing Style

Ex: A = [2 6 9; 4 2 8; 3 0 1];

linearindex = sub2ind(size(A), 3, 2)

linearindex =

6