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E. G. S. Pillay Arts and Science College
(Autonomous), Nagapattinam
Ramanujam Association organizes
“One Day Workshop on MATLAB”
Presentation by
Dr. M. Nuthal Srinivasan, M.E., Ph.D.,
HOD – ME(CS) & Assistant Professor,
Department of ECE, E.G.S.Pillay Engineering College, Nagapattinam

Introduction to Matlab
Rererence: İ.Yücel Özbek

Outline:
What is Matlab?
Matlab Screen
Variables, array, matrix, indexing
Operators (Arithmetic, relational, logical )
Display Facilities
Flow Control
Using of M-File
Writing User Defined Functions
Conclusion

What is Matlab?
• MATRIX Laboratory
• Matlab is basically a high level language which has many
specialized toolboxes for making things easier for us
• How high?
Assembly
High Level
Languages such as
C, Pascal etc.
Matlab

Matlab Screen
• Command Window
• type commands
• Current Directory
• View folders and m-files
• Workspace
• View program variables
• Double click on a variable
to see it in the Array Editor
• Command History
• view past commands
• save a whole session
using diary

Variables
• No need for types. i.e.,
• All variables are created with double precision unless specified
and they are matrices.
• After these statements, the variables are 1x1 matrices with
double precision
int a;
double b;
float c;
Example:
>>x=5;
>>x1=2;

Array, Matrix
• a vector x = [1 2 5 1]
x =
1 2 5 1
• a matrixy = [1 2 3; 5 1 4; 3 2 -1]
y =
1 2 3
5 1 4
3 2 -1
• transpose y = x’ y =
1
2
5
1

Long Array, Matrix
• t =1:10
t =
1 2 3 4 5 6 7 8 9 10
• k =2:-0.5:-1
k =
2 1.5 1 0.5 0 -0.5 -1
• B = [1:4; 5:8]
x =
1 2 3 4
5 6 7 8

Generating Vectors from functions
• zeros(M,N) MxN matrix of zeros
• ones(M,N) MxN matrix of ones
• rand(M,N) MxN matrix of uniformly
distributed random
numbers on (0,1)
x = zeros(1,3)
x =
0 0 0
x = ones(1,3)
x =
1 1 1
x = rand(1,3)
x =
0.9501 0.2311 0.6068

Matrix Index
• The matrix indices begin from 1 (not 0 (as in C))
• The matrix indices must be positive integer
Given:
A(-2), A(0)
Error: ??? Subscript indices must either be real positive integers or logicals.
A(4,2)
Error: ??? Index exceeds matrix dimensions.

Concatenation of Matrices
• x = [1 2], y = [4 5], z=[ 0 0]
A = [ x y]
1 2 4 5
B = [x ; y]
1 2
4 5
C = [x y ;z]
Error:
??? Error using ==> vertcat CAT arguments dimensions are not consistent.

Operators (arithmetic)
+addition
- subtraction
*multiplication
/ division
^power
‘ complex conjugate transpose

Matrices Operations
Given A and B:
Addition Subtraction Product Transpose

Operators (Element by Element)
.* element-by-element multiplication
./element-by-element division
.^ element-by-element power

The use of “.” – “Element” Operation
K= x^2
Erorr:
??? Error using ==> mpower Matrix must be square.
B=x*y
Erorr:
??? Error using ==> mtimes Inner matrix dimensions must agree.
A = [1 2 3; 5 1 4; 3 2 1]
A =
1 2 3
5 1 4
3 2 -1
y = A(3 ,:)
y=
3 4 -1
b = x .* y
b=
3 8 -3
c = x . / y
c=
0.33 0.5 -3
d = x .^2
d=
1 4 9
x = A(1,:)
x=
1 2 3

Basic Task: Plot the function sin(x) between 0≤x≤4π
• Create an x-array of 100 samples between 0 and 4π.
• Calculate sin(.) of the x-array
• Plot the y-array
>>x=linspace(0,4*pi,100);
>>y=sin(x);
>>plot(y)
0 10 20 30 40 50 60 70 80 90 100
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1

Plot the function e-x/3
sin(x) between 0≤x≤4π
• Create an x-array of 100 samples between 0 and 4π.
• Calculate sin(.) of the x-array
• Calculate e-x/3
of the x-array
• Multiply the arrays y and y1
>>y=sin(x);
>>y1=exp(-x/3);
>>y2=y*y1;

Plot the function e-x/3
sin(x) between 0≤x≤4π
• Multiply the arrays y and y1 correctly
• Plot the y2-array
>>y2=y.*y1;
>>plot(y2)
0 10 20 30 40 50 60 70 80 90 100
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7

Display Facilities
• plot(.)
• stem(.)
Example:
>>y=sin(x);
>>plot(y)
>>plot(x,y)
Example:
>>stem(y)
>>stem(x,y)
0 10 20 30 40 50 60 70 80 90 100
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30 40 50 60 70 80 90 100
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7

Display Facilities
• title(.)
• xlabel(.)
• ylabel(.)
>>title(‘This is the sinus function’)
>>xlabel(‘x (secs)’)
>>ylabel(‘sin(x)’)
0 10 20 30 40 50 60 70 80 90 100
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
This is the sinus function
x (secs)
sin(x)

Putting several graphs in one window
• The subplot command creates several plots in a single window.
Here is an example:
• >> t = (0:.1:2*pi)';
• >> subplot(2,2,1)
• >> plot(t,sin(t))
• >> subplot(2,2,2)
• >> plot(t,cos(t))
• >> subplot(2,2,3)
• >> plot(t,exp(t))
• >> subplot(2,2,4)
• >> plot(t,1./(1+t.^2))

Operators (relational, logical)
• == Equal to
• ~= Not equal to
• < Strictly smaller
• > Strictly greater
• <= Smaller than or equal to
• >= Greater than equal to
• & And operator
• | Or operator

Flow Control
• if
• for
• while
• break
• ….

Control Structures
• If Statement Syntax
if (Condition_1)
Matlab Commands
elseif (Condition_2)
Matlab Commands
elseif (Condition_3)
Matlab Commands
else
Matlab Commands
end
Some Dummy Examples
if ((a>3) & (b==5))
Some Matlab Commands;
end
if (a<3)
elseif (b~=5)
end
if (a<3)
else
end

Control Structures
• For loop syntax
for i=Index_Array
Matlab Commands
end
Some Dummy Examples
for i=1:100
end
for j=1:3:200
end
for m=13:-0.2:-21
end
for k=[0.1 0.3 -13 12 7 -9.3]
end

Control Structures
• While Loop Syntax
while (condition)
Matlab Commands
end
Dummy Example
while ((a>3) & (b==5))
end

Use of M-File
Click to create
a new M-File
• Extension “.m”
• A text file containing script or function or program to run

Use of M-File
If you include “;” at the
end of each statement,
result will not be shown
immediately
Save file as Denem430.m

Writing User Defined Functions
• Functions are m-files which can be executed by specifying some
inputs and supply some desired outputs.
• The code telling the Matlab that an m-file is actually a function
is
• You should write this command at the beginning of the m-file
and you should save the m-file with a file name same as the
function name
function out1=functionname(in1)
function out1=functionname(in1,in2,in3)
function [out1,out2]=functionname(in1,in2)

• Examples
• Write a function : out=squarer (A, ind)
• Which takes the square of the input matrix if the input
indicator is equal to 1
• And takes the element by element square of the input matrix
if the input indicator is equal to 2
Same Name

• Another function which takes an input array and returns the sum and product of its
elements as outputs
• The function sumprod(.) can be called from command window or an m-file as

• %%square.m ---- Calculates the square of a number.
• function y = square(x)
• % calculate the square of the given number 'x'
• % Arguments:
• % x (input) value to be squared
• % y (output) the result of the square
• y = x*x;
• end
• % end of square function

Notes:
• “%” is the neglect sign for Matlab (equaivalent of “//”
in C). Anything after it on the same line is neglected by
Matlab compiler.
• Sometimes slowing down the execution is done
deliberately for observation purposes. You can use the
command “pause” for this purpose
pause %wait until any key
pause(3) %wait 3 seconds

Useful Commands
• The two commands used most by Matlab
users are
>>help functionname
>>lookfor keyword

Questions
• ?
• ?
• ?
• ?
• ?

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