technical computing 3

8/14/2019 Technical Computing 3

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TECHNICAL COMPUTING

Qasim Habib


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Todays Content

1. Script Files and Editor/Debugger

2. Programming in MATLAB

3. Relational operators


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Script Files andEditor/Debugger

MATLAB operates in two ways

1.Interactive mode

2.Script files


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Script Files

Script file contains MATLAB commands, sorunning it is equal to typing all the commands one at a time at the command window prompt.

You can run the file by typing its name at thecommand window prompt.

Script file variables are global variables.


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Creating & using a ScriptFile

Following lines show a simple script file

% Program Example.m

% This program computes the sine of

% the square root and displays theresult.

x = sqrt ( [ 5:2:13 ] )

y = sin (x)


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Effective use of Script Files

Used to avoid the need to retypecommonly used procedures.

Names of script files should followthe MATLAB naming conventions.

Script file variables are global ascompared to function file variableswhich are local.


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Debugging Script Files

Debugging a program is the processof finding and removing the bugs,or errors, in a program.

Two type of errors are encountered

1.Syntax errors

2.Runtime errors


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Programming Style

Suggested structure for a script file is

1.Comment Section

2.Input Section3.Calculation Section

4.Output Section


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Controlling input and output


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Example of menu command

Look the use of menu command inthe following example


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Example of fprintf command

Look the use of fprintf command inthe following example


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Task 5

Solve T1.4-2

Study this Topic (optional)

1.5 The MATLAB Help System


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Programming in MATLAB

Programming is performed inMATLAB using script files (m-files).

MATLAB often uses followingcapabilities in programming

1.Relational operators

2.Conditional statements3.Loops


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Relational operators

Relational Operators are used to makecomparisons.

MATLAB has six relational operators to

make comparisons between arrays. Note in the next slide that equal to

operator consist of two equal signs ==,because = sign denotes assignmentoperator in MATLAB.


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Some rules

Comparison is performed onelement-by-element basis

Arrays must be of the samedimension

The result of a comparison usingrelational operator is a logical value,which is either 0 (for false) or 1 (fortrue).


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Examples>> x = [6,3,9] ; y = [14,2,9];

>> z = (x < y)

z =

1 0 0

>> z = (x ~= y)z =

1 1 0

>> z = x (x < y)

z =

6


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The find Function

The function find (x) computes an arraycontaining the indices of the nonzeroelements of the numeric array x.

Example>> x = [-2 0 4]

>> y = find(x)

y =1 3


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Task 6

Example E1.6-1

T1.6-1 & T1.6-2


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Reference

This lecture is from pg 29-46 of your main MATLABbook

INTRODUCTION TO MATLAB 7

FOR ENGINEERS

by

WILLIAM J. PALM III

technical computing 3

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