1. Lab No.03
Structures, logical and
relational operators
Designed by : Dawar Awan
dawar@cecos.edu.pk
CECOS College of Engineering and IT
March – July 2012

2. Relational and logical operators
Relational operators
<
>
<=
>=
==
~=
less than
greater than
less than or equal
greater than or equal
equal
not equal
 Their result will be either true (1) or false (0)
 >> 3 < 5
returns 1
 >> a = 3 == 5
returns 0
 These operators when applied on matrices, returns 1s and 0s in
a resultant matrix
CECOS College of Engineering and IT
March – July 2012

3. Relational and logical operators
>> A = [ 1 2; 3 4 ];
>> B = [ 6 7; 8 9 ];
>> A == B
ans =
0 0
0 0
>> A < B
ans =
1 1
1 1
CECOS College of Engineering and IT
March – July 2012

4. Relational and logical operators
Logical operators
&
and
|
or
~
not
 Try the following commands
>> ~A
>> A | ~A
>> A&B
>> A | B
>> A & ~B
CECOS College of Engineering and IT
March – July 2012

5. Control structures
 Structures are used to control the sequence of
execution of code. This is achieved by using
 Conditional control structures
 Looping control structures
 Logical and relational operators are used in
implementing the control structures.
CECOS College of Engineering and IT
March – July 2012

6. Conditional Control structures
 Following are some conditional/branching control
structures
i- if-end Construct : The most basic construct is
if <condition>
<program>
end
Example
a = 1;
b = 2;
if a < b
c = 3;
end;
CECOS College of Engineering and IT
March – July 2012

7. Conditional Control structures
ii- If-else-end Construct
if <condition1>
<program1>
else
Example
a = 1;
b = 2;
<program2>
if a < b
end
c = 3;
else
c=10;
end;
CECOS College of Engineering and IT
March – July 2012

8. Conditional Control structures
iii- If-elseif-end Construct: Another variation is
if <condition1>
<program1>
elseif <condition2>
<program2>
end
CECOS College of Engineering and IT
Example
a = 1;
b = 2;
if a < b
disp(‘b is greater’);
elseif (a>b)
disp(‘a is greater’);
else
disp(‘ a and b are equal’);
end;
March – July 2012

9. Looping Control structures
i- For loop
for i= 1 : n
<program>
end
For each value of ‘i’ , “program” executes one time i.e the program
will execute n-times
>> for i = 1 : 5
c = 2*i
end
c=2
c = 4 ….
CECOS College of Engineering and IT
… ….
…. c = 10
March – July 2012

10. Looping Control structures
Any vector can be used for the value of i
for i = [2,4,5,6,10]
<program>
end
CECOS College of Engineering and IT
March – July 2012

11. Looping Control structures
ii- Nested For loop
for i=1:3
for j=1:3
A(i,j) = i+j;
Program
end
end
For each value of ‘i’ , “program” executes three times i.e the
program will execute 9 times.
A(1,1)=1+1
A(1,2)=1+2
A(1,3)=1+3
A(2,1)=2+1
……
….
…
A(3,3)=3+3
…..
CECOS College of Engineering and IT
…..
….
March – July 2012

12. While loops
while <condition>
<program>
end
 The ‘program’ executes till the ‘condition’ remains true,
and stops when the ‘condition’ becomes false
CECOS College of Engineering and IT
March – July 2012

13. Task
1. Create an m-file that finds the factorial of a number using for
loop (don’t use the built in function ‘factorial’).
2. Repeat the above question for while loop.
3. Generate square of first ten integers using for loop.
4. Add the following two matrices using nested for loop.
CECOS College of Engineering and IT
March – July 2012

14. Task
5. Using MATLAB, Find the value of C, where C is defined as
follows:
C= 10a
,
0<a<=5
C= 20a
,
5<a<=10
The value of ‘a’ shall be provided by the user.
6. Using MATLAB, List all the values of y, for 0 ≤ n ≤ 10. if
y=n2
,
n is even
y=n
,
n is odd
CECOS College of Engineering and IT
March – July 2012