4.cece matlab programming

8/3/2019 4.Cece Matlab Programming

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MATLABCECE ACADEMIC TEAM

Prepared by: Mohamed Farag


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Contents

Intro to Programming

Flow Control Conditional Statements.

Loops.

M-Files. Scripts Vs M-Functions

New Data Types Multidimensional Arrays

Structures Cell Arrays

Error Handling

19/7/2011Matlab CECE Academic Team


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Design of computer programs to solve complexproblems needs to be done in a systematic mannerfrom the start to avoid time-consuming and

frustrating difficulties later in the process. Programming Types

Algorithms and Control Structures

Structured ProgrammingOOP Programming


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Algorithms and Control Structures

an ordered sequence of precisely defined instructions thatperforms some task in a finite amount of time

There are three main categories of algorithmic operations: Sequential Operation

Conditional Operation

Iterative Operation


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Structured Programming

A technique for designing programs in which a hierarchy ofmodules is used, each having a single entry and a single exitpoint, and in which control is passed downward through thestructure without unconditional branches to higher levels of thestructure.

In MATLAB these modules can be built-inor user-definedfunctions.


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OOP Programming

Four main concepts

Encapsulation

Data Hiding Inheritance

Polymorphism


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Flow Control


Logical Operation

~ : not

& : And

| : Or

&& : Short circuit And ( Scalar operation)

|| : Short Circuit Or ( Scalar Operation)

Note:- ~:not operation is an element-wiseoperation(it affects each element in the array )


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Flow Control


Rational Operation

==:equal

< : less than

> : greater than

= : greater than or equal

~= : not equal


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Flow Control


Masking

If we want to do a specific operation on specific elementsunder certain conditions.

We have two ways: Using loops and loop over the array and check the condition on

each element then do your operation

Using Masks

Ex:

A=[1 2 3;-1 -2 -3;4 5 6]; A(A


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Flow Control


Conditional Statements

IF Conditionally execute statements.

The general form of the IF statement is

IF expression

statements

ELSEIF expression

statementsELSE

statements

END

Example

if I == J

A(I,J) = 2;

elseif abs(I-J) == 1

A(I,J) = -1;

else

A(I,J) = 0;

end


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Flow Control


Conditional Statements

SWITCH Switch among several cases based on expression.

The general form of the SWITCH statement is:

SWITCH switch_expr

CASE case_expr,

statement, ..., statement

CASE {case_expr1, case_expr2, case_expr3,...}


OTHERWISE,


END


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Flow Control


Example

t = [0 : 100]; x = exp(-t) . *sin(t);

response = input( 'Type min, max , or sum .',' s ' )

response = lower ( response ) ;

switch response

case min

minimum = min (xl

Case max

maximum = max (x)

case sum

total = sum(x)

otherwise

disp ( ' You have not entered a proper choice . )

End


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Flow Control


Loops For Repeat statements a specific number of times.

The general form of a FOR statement is:

FOR variable = expr, statement, ..., statement END

Example

for R = 1:N

for C = 1:N

A(R,C) = 1/(R+C-1);

end

end


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Flow Control


WHILE Repeat statements an indefinite number of times.

The general form of a WHILE statement is:

WHILE expression

statements

END

Ex:- x = 1

while x


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Flow Control


The break statement. A while loop can be terminated with thebreak statement, which passes control to the first statementafter the corresponding end. The break statement can also beused to exit a for loop.

The continue statement can also be used to exit a for loop to

pass immediately to the next iteration of the loop, skipping theremaining statements in the loop.


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M-Files.


M-Files can be used to write Scripts & Functions

Functions

need input & output arguments

Variables are local Scripts

Variables are global

Can be called by writing its name in the command window


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M-Files.


Functions:-

Style

Function [Outputs]=function_name(inputs)

% discription of the Function it will be displayed when youuse help function_name

Function body


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M-Files.


Functions Types:-

Primary Function

Ex:-

function [mean,stdev] = stat(x) %STAT Interesting statistics.

n = length(x);

mean = sum(x) / n;

stdev = sqrt(sum((x - mean).^2)/n);


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M-Files.


Functions Types:- Subfunctions:-

Function defined in the same primary function file and used inside it. itis not visible outside the file.

Ex:- function [mean,stdev] = stat(x) %STAT Interesting statistics. n = length(x); mean = avg(x,n); stdev = sqrt(sum((x-avg(x,n)).^2)/n);

%------------------------- function mean = avg(x,n) %AVG subfunction mean = sum(x)/n


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New Data Types


Multidimensional Array

It is an array but with more than two subscripts

Ex:- A=ones(3,5,2);

Used for 3D data like:

Temperature in a room

A sequence of Matrix


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New Data Types


Cell Array

A cell array is a collection of containers called cells inwhich you can store different types of dataSome

functions Cell:create empty cell array

Celldisp:display cell array

Cellplot:display grahpical representation of cell array


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New Data Types


Structures

Multidimensional arrays accessed by textual fielddesignators

Ex:- S.name=mohamed;

S.score=83;

S.grade=A+;

Or :- s=struct(name,mohamed,score,83,grade,A+);


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Error Handling


Try- Catch Ex:-

function matrixMultiply(A, B)

try

A * B

catch err = lasterror;

if(strfind(err.message, 'Inner matrix dimensions'))

disp('** Wrong dimensions for matrix multiply')

Else

if(strfind(err.message, 'not defined for values of class'))

disp('** Both arguments must be double matrices') end

end

end


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References

[1] Using Matlab version 6 , Mathworks

[2] Introduction to Matlab 7 for engineers, William J

[2] David F. Griffiths , An Introduction to Matlab.

[3] Matlab Help.



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THANK YOU!Prepared by: Mohamed Farag

Email: [email protected]

4.cece matlab programming

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