matlab loops

MATLAB Applications to electrical Engineering

9/2/2015 11:09:45 PM MATLAB PRESENTATION 1

V R SIDDHARTHA ENGINEERING COLLEGE

EEE DEPARTMENT

S.V.R.LAKSHMI KUMARI ASSOCIATE PROFFSSOR

P.VENKATESH ASSISTANT PROFESSOR

Introduction to MATLAB Matlab Basics

Vectors and Matrices

Plots

Loops

MATLAB examples

Control Flow

If Conditionally execute statements

Else IF statement condition

Elseif IF statement condition

end Terminate scope of FOR, WHILE, SWITCH, TRY and IF ...

for Repeat statements a specific number of times

While Repeat statements an indefinite number of times

Break Terminate execution of WHILE or FOR loop

Switch Switch among several cases based on expression

Case SWITCH statement case

9/2/2015 11:09:46 PM 3 MATLAB PRESENTATION

Boolean operators in MATLAB Symbol Meaning Example

==

~=

>

>=

<

y

if x>=c

if x3)

if x~=y

The operators AND, OR, NOT allow you to combine simpler tests 4

Decision making in MATLAB

For simple decisions?

IF END `

More complex decisions?

IF ELSEIF ELSE ... END


Control Structures

If Statement Syntax if (Condition_1) Matlab Commands elseif (Condition_2) Matlab Commands elseif (Condition_3) Matlab Commands else Matlab Commands end

if ((a>3) & (b==5)) Some Matlab Commands; end if (a

if thenelse end EXAMPLE : TO CHECK THE NUMBER EVEN OR ODD % Generate a random number %Check whether it is even %display that it is even if it is even %display that it is odd if it is not even a = randi(100, 1); Disp(a) if rem(a, 2) == 0 %use shift+enter disp('a is even') else disp('a is odd') end


If and Switch The switch statement and the if statement are equally powerful,but the switch statement is especially well suited to handle cases with only a finite set of choices


if-elseif-else construction

if

elseif

else

end

if height>170

disp(tall)

elseif height

if-constructs can be interleaved:

if a==b

if b==0

disp(b=0);

end;

else

disp(b is not equal to a);

end;


Program to calculate your internal marks MATLAB code: clear clc a1=input('enter assignment1 marks::'); a2=input('enter assignment2 marks::'); s1=input('enter assignment1 marks::'); s2=input('enter assignment2 marks::'); amax=max(a1,a2); amin=min(a1,a2); a=((2/3)*amax+(1/3)*amin); smax=max(s1,s2); smin=min(s1,s2); s=((2/3)*smax+(1/3)*smin); atten=input('enter percentage of attendance::'); if(atten75)&(atten80)&(atten90)&(atten

FOR LOOPS While Loops

Finite (will run a specified number of times, as determined when the loop is first executed)

Indefinite (will run until a given logical or relational condition evaluates to false or 0)

Built in Index (Matlab will define and Increment an index automatically)

User Defined Index (You have to define an index before the loop and increment the index inside the body of the loop)


Control Structures

For loop syntax

for i=Index_Array

Matlab Commands

end

Examples: for i=1:100 Some Matlab Commands; end for j=1:3:200 Some Matlab Commands; end for m=13:-0.2:-21 Some Matlab Commands; end for k=[0.1 0.3 -13 12 7 -9.3] Some Matlab Commands; end


Program: To initialize each element of a to 1 for i=1:10 a(i)=1; End Output : a = 1 1 1 1 1 1 1 1 1 1


while loop

While Loop Syntax

while (condition)

Matlab Commands

end

Dummy Example while ((a>3) & (b==5)) Some Matlab Commands; end


Program: To initialize each element of a to 1 using while loop i=1; while i

FOR and WHILE

sum=0;

for i=1:10

sum=sum+i;

end

disp(sum)

sum=0; i=0; while i

Switch-case Selection Switch conditional structures is particularly useful when dealing

with some kind of menu where a variable can take a set of values and various actions must take place accordingly.

The syntax is:

switch variable

case value1

do this

case value2

do that

end;


Example of using switch

day=4; %This corresponds to Thursday=4th day

%after Monday

switch day

case 1 %this effectively means if day==1

disp(Today is Monday);

case 2 % i. e. if day==2

disp(Today is Tuesday);

otherwise

disp(The number should be between 1 and 7)

end;

Note: The otherwise statement is optional. If it isnt there and the variable doesnt take any of the case values tested then Matlab reaches end and nothing has happened.


In general, when you have many possible discrete, known values, switch statements are easier to read than if statements


Nested loops

If one loop is completely inside another one ,then the two loops are called nested loops

Example : calculate the product of two integers MATLAB CODE :

for i=1:3

for j=1:3

product=i*j;

fprintf('%d*%d=%d\n',i,j,product);

end

end


Output : 1*1=1 1*2=2 1*3=3 2*1=2 2*2=4 2*3=6 3*1=3 3*2=6 3*3=9


If a break statement appears inside a set of nested loops ,then the break statement refers to the innermost of the loops containing it

Example : for i=1:3 for j=1:3 if j==3; break; end product=i*j; fprintf('%d*%d=%d\n',i,j,product); end fprintf('End of inner loop\n'); end fprintf('End of outer loop\n');


Output : 1*1=1 1*2=2 End of inner loop 2*1=2 2*2=4 End of inner loop 3*1=3 3*2=6 End of inner loop End of outer loop


Commands and Functions

The break and continue Statements:

Example :

for i=1:5

if i==3;

break

end

fprintf('i=%d\n',i);

end

disp('end of loop');

Break statement

Output: i=1 i=2 end of loop

continue statement

Example : for i=1:5

if i==3;

continue

end

fprintf('i=%d\n',i);

end

disp('end of loop');

Output: i=1 i=2 i=4 i=5 end of loop

matlab loops

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