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NET 222: COMMUNICATIONS AND
NETWORKS FUNDAMENTALS
(PRACTICAL PART)
Networks and
Communication
Department
Lab 1 : Introduction to MatlaB
Lecture Contents
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Matlab introduction
Why Matlab
Matlab Software install and interface
Matlab Variables
Matlab Matrices
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Matlab introduction
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MatLab : Matrix Laboratory
Numerical Computations with matrices
 Every

number can be represented as matrix
Why Matlab?
 User
Friendly (GUI)
 Easy to work with
 Powerful tools for complex mathematics
 It was originally designed for solving linear algebra type
problems using matrices
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Why Matlab?
Graphing
 A Comprehensive array of plotting options
available from 2 to 4 dimensions
 Full control of formatting, axes, and other visual
representational elements
Why Matlab?
Multi-platform, Multi Format data importing
 Data can be loaded into Matlab from almost
any format and platform
 Analog/Digital Data files
PC
100101010
UNIX
Subject 1 143
Subject 2 982
Subject 3 87 …
Matlab Software install
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Matlab Interface
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Title bar
Menu bar
help
Current working Directory
Current Directory
contents
command window
File details
Workspace(variable
list)
Function Catalog
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Matlab Interface
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Title bar
Menu bar
help
Current working Directory
The MATLAB environment is command oriented
Current Directory
contents
command window
File details
Workspace(variable
list)
Function Catalog
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Matlab Interface
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Title bar
help
Menu bar
Current working Directory
View folders and m-files
Current Directory
contents
command window
type commands
Command History
view past commands save a
whole session using diary
File details
Workspace(variable
list)
Function Catalog
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To appear Command History, select layout
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All MATLAB windows are docked in the default desktop,
which means that they are tiled on the main MATLAB
window.
Docked
window
Undocked
window
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Command window
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MATLAB expressions and
statements are evaluated as
you type them in the
Command Window, and
results of the computation
are displayed there too.
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Variables
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No need for types. i.e.,
int a;
double b;
float c;
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All variables are created with double precision unless specified
and they are matrices.
Example:
>>x=5;
>>x1=2;
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After these statements, the variables are 1x1 matrices with
double precision
Creating Variables
 Names
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Can be any string of upper and lower case letters along with numbers
and underscores but it must begin with a letter
Reserved names are IF, WHILE, ELSE, END, SUM, etc.
Names are case sensitive
 Value

This is the data the is associated to the variable; the data is accessed
by using the name.
Example of Value : Singletons
 To
assign a value to a variable use the equal symbol
‘=‘
>> A = 32
 To
find out the value of a variable simply type the
name
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The value of two variables can be added together, and
the result displayed…
>> A = 10
>> A + A
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or the result can be stored in another variable
>> A = 10
>> B = A + A
Matlab Assignment &Operators
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Assignment =
Addition +
Subtraction Multiplication * or.*
Division / or ./
Power ^ or .^
' transpose
a = b (assign b to a).
a+b
a -b
a*b or a.*b
a/b or a./b
a^b or a.^b
a'
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Variables are assigned numerical values by typing the
expression directly.
for example a = 1+2
yields: a = 3
The answer will not be displayed when a semicolon is put at the
end of an expression, for example
a = 1+2; (no answer)
 For example, since “a” was defined previously, the following
expression is valid b = 2*a
yields: b = 6
Matrices
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A MATLAB matrix is a rectangular array of numbers
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Scalars and vectors are special cases of matrices
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MATLAB allows you to work with a whole array at a time
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Scalar: A matrix with one row and one column.
A = [3.5]
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Vector: A matrix with one row (a row vector) or one column, ( a column
vector). Use square brackets [] to contain the numbers
Note that in MATLAB the first index of a vector or
matrix starts at 1, not 0 as is common with other
programming languages.
A matrix can be created in MATLAB as follows
(note the commas AND semicolons):
matrix = [1 , 2 , 3 ; 4 , 5 ,6 ; 7 , 8 , 9]
matrix =
123
456
789
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a vector
x = [1 2 5 1]
x =
1

2
transpose
5
1
y = x’
y =
1
2
5
1
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a matrix
x = [1 2 3; 5 1 4; 3 2 -1]
x =
1
5
3
2
1
2
3
4
-1
Long Array, Matrix
t =1:10
t =
k
1
=2:-0.5:-1
2
3
4
1.5
1
0.5
5
6
7
8
k =
2
B
= [1:4; 5:8]
B =
1
5
2
6
3
7
4
8
0
-0.5
-1
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Extracting a Sub-Matrix
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A portion of a matrix can be extracted and stored in a
smaller matrix by specifying the names of both matrices
and the rows and columns to extract.
The syntax is:
where r1 and r2 specify the beginning and ending
rows and c1 and c2 specify the beginning and ending
columns to be extracted to make the new matrix.
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Matlab Matrices
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• A column vector can be
extracted from a matrix.
As an example we
create a matrix below:
• Here we extract column
2 of the matrix and
make a column vector:
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Matlab Matrices
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A row vector can be
extracted from a matrix.
As an example we
create a matrix below:
Here we extract row 2 of the
matrix and make a row
vector. Note that the 2:2
specifies the second row
and the 1:3 specifies which
columns of the row.
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Matrix Index
The matrix indices begin from 1 (not 0 (as in C))
The matrix indices must be positive integer
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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
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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.
Some matrix functions in Matlab
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X = ones(r,c)
X = zeros(r,c)
A = diag(x)
[r,c] = size(A)
+-*/
.+ .- .* ./
v = sum(A)
% Creates matrix full with ones.
% Creates matrix full with zeros.
% Creates squared matrix with
vector x in diagonal.
% Return dimensions of matrix A.
% Standard operations.
% Wise addition, substraction ,…
% Vector with sum of columns.
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Example of Function
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
Example
>>x=(0:0.1:1)'
>>y=sin(x)
>>[x y]
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
A = [1 2 3; 5 1 4; 3 2 1]
A=
1 2 3
5 1 4
3 2 -1
x = A(1,:)
x=
c=x./y
d = x .^2
b=
c=
0.33 0.5 -3
d=
y = A(3 ,:)
y=
1 2 3
b = x .* y
3 8 -3
3 4 -1
K= x^2
Erorr:
??? Error using ==> mpower Matrix must be square.
B=x*y
Erorr:
??? Error using ==> mtimes Inner matrix dimensions must agree.
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Functions
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MATLAB has many built-in functions.
Some math functions are:
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Matlab Special Variables
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ans: default variable name
pi: ratio of circle circumference to its diameter, π =
3.1415926...
eps: smallest amount by which two numbers can differ
inf or Inf : infinity
nan or NaN : not-a-number, e.g. 0/0
date: current date in a character string format, such as
19-Mar-1998.
Commands involving variables:
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who: lists the names of defined variables
whos: lists the names and sizes of defined variables
clear: clears all variables, resets default values of special variables
clear var: clears variable var
clc: clears the command window, homes the cursor (moves the prompt
to the top line), but does not affect variables.
clf: clears the current figure and thus clears the graph window.
more on: enables paging of the output in the command window.
more off: disables paging of the output in the command window.
Note
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The '%' sign indicates that there is a comment in
that line and Matlab does not do anything with it. It
is as if it were inexistent, and it exists only for
explanatory purposes.
“%” is the neglect sign for Matlab (equaivalent of
“//” in C).
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Useful Commands

The two commands used most by Matlab
users are
>>help functionname
>>lookfor keyword
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The End
Any Questions ?
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