Technical Computing: Qasim Habib

TECHNICAL COMPUTING

Qasim Habib

Today’s Content 1. Script Files and Editor/Debugger 2. Programming in MATLAB 3. Relational operators

Script Files and Editor/Debugger MATLAB operates in two ways 1.Interactive mode 2.Script files

Script Files • Script file contains MATLAB commands, so running 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 the command window prompt. • Script file variables are global variables.

Creating & using a Script File • Following lines show a simple script file % Program Example.m % This program computes the sine of % the square root and displays the result. x = sqrt ( [ 5:2:13 ] ) y = sin (x)

Effective use of Script Files • Used to avoid the need to retype commonly used procedures. • Names of script files should follow the MATLAB naming conventions. • Script file variables are global as compared to function file variables which are local.

Debugging Script Files • Debugging a program is the process of finding and removing the “bugs”, or errors, in a program. • Two type of errors are encountered 1.Syntax errors 2.Runtime errors

Programming Style Suggested structure for a script file is 1.Comment Section 2.Input Section 3.Calculation Section 4.Output Section

Controlling input and output

Example of menu command • Look the use of menu command in the following example

Example of fprintf command • Look the use of fprintf command in the following example

Task 5 • Solve T1.4-2 • Study this Topic (optional) 1.5 The MATLAB Help System

Programming in MATLAB • Programming is performed in MATLAB using script files (m-files). • MATLAB often uses following capabilities in programming 1.Relational operators 2.Conditional statements 3.Loops

Relational operators • Relational Operators are used to make comparisons. • 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 ‘assignment operator’ in MATLAB.

Some rules • Comparison is performed on element-by-element basis • Arrays must be of the same dimension • The result of a comparison using relational operator is a logical value, which is either 0 (for false) or 1 (for true).

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

The find Function • The function find (x) computes an array containing the indices of the nonzero elements of the numeric array x. • Example >> x = [-2 0 4] >> y = find(x) y = 1 3

Task 6 • Example E1.6-1 • T1.6-1 & T1.6-2

Reference This lecture is from pg 29-46 of your main MATLAB book

INTRODUCTION TO MATLAB 7 FOR ENGINEERS by WILLIAM J. PALM III