Matlab Basic

Dr. Imtiaz HussainAssociate Professoremail: imtiaz.hussain@faculty.muet.edu.pkURL :http://imtiazhussainkalwar.weebly.com/

2

MATLAB Product Family

3

Basic Commands

4

Entering & Quitting MATLAB

• To enter MATLAB double click on the MATLAB icon.

• To Leave MATLAB Simply type quit and press enter.>> quit

5

Some Basic Commands

• To check the list of installed toolboxes type

>>ver

• To clear the screen type

>>clc

• To move the cursor to upper left corner of the command window type

>>home

6

Some Basic Commands (contd…)

• To list the current variables type

>>who

• To list the current variables in long form type

>>whos

• To clear the workspace type

>>clear

• To remove particular variable from the workspace type

>> clear ‘name of the variable’

7

Some Basic Commands (contd…)

• To get list of Help topics type

>>help

• To get help for any topic type

>>help ‘topic’

• To get help for any command type

>>help ‘command/syntax’

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Some Basic Commands (contd…)

• To search command type

>>lookfor ‘keyword’

• To list the files in a directory type

>>dir ‘directory name’

• To list the Matlab files only type

>>what ‘directory name’

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Working With MATLAB Variables

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Types of MATLAB Variables

• Scalar

– 1x1 array

• Vector

– nx1 (column vector) or 1xn (row vector)

• Matrix

– mxn

• Character Arrays (Strings)

11

Defining Scalars

Variables are assigned numerical values by typing the expression directly, for example, typing

>> a = 2

yields:

a =

2

12

Variable Definitions

We can also assign numerical values to the variables by typing the expression

>> b = 1+2

yields:

b = 3

13

Variable Definitions

• After typing the expressions the answers are

echoed back.

• To suppress the echo put semicolon at the end

of the expression.

>> c = 5;

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Arithmetic Operators on Scalars

• MATLAB utilizes the following arithmetic operators:

 

+ ADDITION

 -  SUBTRACTION

 *  MULTIPLICATION

 /  DIVISION

 

^

 POWER

OPERATOR

 

15

Variable Definition (Contd…….)

A variable can be assigned using a formula. For example, since a was defined previously, the following expression is valid

>> d = 2*a

yields:

d =

4

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Variables in Workspace

• Type who to check the stored variables in workspace.

>> who

Your variables are:

a b c d

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Variables in Workspace

• Type whos to check the stored variables in long form.

>> whos

Name Size Bytes Class

a 1x1 8 double array b 1x1 8 double array c 1x1 8 double array d 1x1 8 double array

Grand total is 4 elements using 32 bytes

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Complex numbers

• A complex number 3+2i in Matlab is entered in the following form

>> 3+2*i

Or

>> 3+2*j

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Complex numbers

• An exponential number 3x10-2 in Matlab is entered in the following form

>> 3e-2

Yields:

ans=

0.0300

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Exercise#1

Investigate the effect of following commands

(i) k=3 (ii) f= 2*c/3 (iii) g=c*d^2

(iv) h=c-d+k (v) who (vi)

whos

(vii) clear (viii) who (ix) whos

(x) 3x10-5+5j

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Defining Vectors

• Row Vectors

– 1xn

• Column Vectors

– nx1

naaaA ...21

nb

b

b

B

.

.

.2

1

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Defining Row Vectors

To create a row vector A simply type in:

A = [2 0 1 4 7 1 5 6 4]

1x9 vectorA =2 0 4 7 1 5 6 411 2 3 4 5 6 7 8 9

A(5)A(2)

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Defining Row Vectors

v = [2 0 1 4 7 1 5 6 4]

1x9 vectorA =2 0 4 7 1 5 6 411 2 3 4 5 6 7 8 9

A(6:9)A(1:4)

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Defining Column Vectors

To create a column vector B simply type in:

B = [3; 5; 0; 0; 1; 4; 9; -1; 1]

1-1

9

4

10

0

5

3 1

2

3

4

5

6

7

8

9

B = 9x1 vector

B(5)

B(3)

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Defining Column Vectors

B = [3; 5; 0; 0; 1; 4; 9; -1; 1]

1-1

9

4

10

0

5

3 1

2

3

4

5

6

7

8

9

9x1 vector

B(7:9)

B(2:5)

B =

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Arithmetic Operators (Arrays)

 + ADDITION

 - SUBTRACTION

 .* ARRAY MULTIPLICATION

 ./ ARRAY DIVISION

 .^ ARRAY POWER OPERATOR

 ' TRANSPOSE

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Exercise#2Investigate the effect of the following commands:

V=[2 4 7 5] and w=[1 3 8 9]

(i) v(2) (ii) sum = v + w (iii) diff = v – w

(iv) vw = [v w] (v) vw(2: 6) (vi) v’

(vii) v./w (viii) v.*w (ix) whos

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Exercise#3

Investigate the effect of the following commands.

z=[1; 1; 0; 0]

(i) z’ (ii) z*v

(iii) [v; w] (iv) v*z

(v) [z; v’] (vi) z + v’

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Defining Matrices

A Matrix is a mxn array

mnmm

n

n

aaa

aaa

aaa

M

....

.

.

.

.

.

.

.

.

.

.

....

...

21

22221

11211

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Defining Matrices

To enter the matrix

43

21M

The most obvious ways are to type

M = [1 2; 3 4]

or

M = [ [1 3]’ [3 4]’ ]

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Defining Matrices

0391

8147

4713

1931

N

1 3

3 1

9 1

7 4

7 4

1 9

1 8

3 0

1

2

3

4

5

8

9

6

7

10

11

12

14

15

16

13

N =

N(1,3) or N(9)

N(4,3) or N(12)

N=[1 3 9 1; 2 1 7 4; 7 4 1 8; 1 9 3 0]

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Defining Matrices

0391

8147

4713

1931

N

1 3

3 1

9 1

7 4

7 4

1 9

1 8

3 0

1

2

3

4

5

8

9

6

7

10

11

12

14

15

16

13

N =

N(1:4)

N(10:12)

N=[1 3 9 1; 2 1 7 4; 7 4 1 8; 1 9 3 0]

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Defining Matrices

0391

8147

4713

1931

N

1 3

3 1

9 1

7 4

7 4

1 9

1 8

3 0

1

2

3

4

5

8

9

6

7

10

11

12

14

15

16

13

N =

N(1:2,1:2)

N(3:4,3:4)

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Defining Matrices

0391

8147

4713

1931

N

1 3

3 1

9 1

7 4

7 4

1 9

1 8

3 0

1

2

3

4

5

8

9

6

7

10

11

12

14

15

16

13

N =

N(:,1:2)

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Defining Matrices

0391

8147

4713

1931

N

1 3

3 1

9 1

7 4

7 4

1 9

1 8

3 0

1

2

3

4

5

8

9

6

7

10

11

12

14

15

16

13

N =

N(3:4,:)

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Exercise#4Investigate the effect of the following commands:

(i) N’ (ii) M*N (iii) M/N

(iv) M + N (v) M*z(1:2) (vi) v(3:4)*M

(vii) M(1,1) (viii) M(1:2,1:2) (ix) M(:,1)

(x) M(2,:)

M=[1 2; 3 4] N=[-1 3; 5 2]

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Exercise#5

Investigate the effect of the following commands:

(i) K = inv(M) (ii) I = eye(2) (iii) rank(M)

(iv) Zeros(3) (v) Zeros(3,2) (vi) ones(4)

(vii) ones(4,5) (viii) tril(M) (ix) triu(M)

(x) diag(M) (xi) size(M) (xii) det(M)

(xiii) eig(M) (xiv) magic(3)

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21MM=[1 2; 3 4]

Exercise#6

1) Define a matrix A of dimension 2 x 4 whose (i,j) entry is A(i,j)=i+j

2) Extract two 2 x 2 matrices A1 and A2 out of the matrix A. A1 contains the

first two columns of A, A2 contains the last two columns of A

3) Compute the matrix B to be the sum of A1 and A2

4) Compute the eigen values and eigen vectors of B

5) Compute the determinant of B

6) Compute the inverse of B

7) Compute the rank of B

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Defining Character Arrays (Strings)

Character arrays are created using single quote delimiter

>> str = ‘MATLAB‘

Yields

str =

MATLAB

1x6 vectorstr = M A L A BT1 2 3 4 5 6

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Defining Character Arrays (Strings)

>> str = ‘MATLAB‘

str = M A L A BT1 2 3 4 5 6

str(3)str(5:6)

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Conversion B/W Numeric & String Arrays

• To convert from numeric to string array

– num2str

• To convert from string array to numeric array

– str2num

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Numeric to string conversion

>> num=120;

>> strnum=num2str(num);

>> whos

Name Size Bytes Class

strnum 1x3 6 char array num 1x1 8 double array

Grand total is 4 elements using 14 bytes

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String to Numeric conversion

>> str=‘1330’;

>> num=str2num(str);

>> whos

Name Size Bytes Class

num 1x1 8 double array str 1x4 8 char array

Grand total is 5 elements using 16 bytes

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QUESTIONSThank you for your concentration