Introduction to MATLAB

Transcription

1 Chapter 1 Introduction to MATLAB MATLAB Matrix Laoratory A special-purpose program optimized to perform engineering and scientific calculations Chapter M1: Introduction to MATLAB 1

2 MATLAB Integrated development environment Built-in functions & liraries Toolkits in various specialties Built-in deugger Extensive online help Graphics User Interface Rapid prototyping of new programs Why MATLAB? Industry standard software application Wealth of uilt-in functions and liraries Over 1,000 functions in asic MATLAB alone Tooloxes (add-on software modules) image & signal processing, control systems design, fuzzy logic, etc. Has own structured programming language Ease of application and testing (pre- and post-processing without lots of programming and formatting) Platform independent Chapter M1: Introduction to MATLAB 2

3 What is MATLAB? Both a computer programming language and a software Began as a set of tools to solve linear algeraic equations. Has grown to a complete scientific programming suite Interpretive programming language: Read script files and perform operations; generally not compiled Enhanced calculator / spreadsheet much more flexile Complete visualization package and post-processing analysis suite Advantage of MATLAB 1. Ease of Use Built-in integrated development environment and MATLAB deugger Ideal for rapid prototyping of new programs 2. Platform Independence Windows 10, Linux, Unix, Macintosh, etc. 3. Predefined Functions 4. Device-Independent Plotting 5. Graphical User Interface (GUI) 6. MATLAB Compiler Chapter M1: Introduction to MATLAB 3

4 Disadvantage of MATLAB Slow It is an interpreted language, usually execute more slowly than compiled languages Can e mitigated y using MATLAB compiler Expensive 5-10 times more expensive than conventional C or Fortran compilers Inexpensive Student Edition availale MATLAB Environment MATLAB Desktop The Command Window The Command History Window The Start Button The Documents Window including Editor/Deugger and Array Editor The Figure Window The Workspace Browser The Help Browser The Path Browser Chapter M1: Introduction to MATLAB 4

5 MATLAB Windows Command Window -- enter commands and data -- print results Figure Window -- display plots and graphs Edit Window -- create and modify M-files Managing MATLAB Environment who or whos -- See current runtime environment clear -- remove all variales from memory clc -- clear the command window clf -- clear the graphics window save -- save the workspace environment load -- restore workspace from a disk file aort -- CTRL-C help -- help command Really good help command Chapter M1: Introduction to MATLAB 5

6 Getting Help 1. Help Browser select from the desktop toolar Type helpdesk or helpwin in command window 2. help function name Search for an exact function name match 3. lookfor function name Slower, ut improves the chances of getting ack useful information MATLAB Search Path 1. Look for the name as a variale. If found, display the current contents of the variale 2. Look for the name as an M-file in the current directory. Executes the function or command if a match is found 3. Look for M-file in any directory in the search path. Executes the function or command. Never use a variale with the same name as a MATLAB function. Never create an M-file with the same name as a MATLAB function or command. Chapter M1: Introduction to MATLAB 6

7 Directory and File Management pwd: show (print) current working directory mkdir: make new directory rmdir: remove directory cd: change current working directory dir: list directory delete: delete file or graphics oject copyfile: copy file or directory movefile: move file or directory Using MATLAB as a Scratch Pad Similar to a calculator Perform calculations y typing the formula directly into the Command Window x Evaluate and plot y e sin(10 x), 0 x» x=0:0.01*pi:pi;» y=exp(-x).*sin(10*x);» plot(x,y) Chapter M1: Introduction to MATLAB 7

8 Scalar Arithmetic Operations Symol Operation MATLAB Form Addition: a a - Sutraction: a- a * Multiplication: a a* / Right Division: a/ a a/ \ Left Division: a\ a a\ ^ Exponentiation: a a^ Examples: x = (a + *c)/d^2 count = count + 1 (Matrix inverse) Order of Precedence of Arithmetic Operations 1. Parentheses, starting with the innermost pair 2. Exponentiation, from left to right 3. Multiplication and division with equal precedence, from left to right 4. Addition and sutraction with equal precedence, from left to right Examples: factor = 1 + /v + c/v^2 slope = (y2 - y1)/(x2 - x1) loss = f * length/dia * (1/2 * rho * v^2) func = *(3*x^4 + (x + 2/x)^2) Chapter M1: Introduction to MATLAB 8

9 MATLAB MATLAB is a numerical analysis system Can write programs, ut they are not formally compiled Should still use structured programming Should still use comments Comments are indicated y % at the eginning of the line Program Documentation Comments!!! You must include comments in the computer programs you turn in -- otherwise we will have great difficulty knowing what you are doing Chapter M1: Introduction to MATLAB 9

10 For example, here is some cryptic code without comment for j=0:2 end k=(2-j)*(1+3*j)/2 What does it do? Put a comment in % turns (0,1,2) into (1,2,0) MATLAB Syntax No complicated rules Perhaps the most important thing to rememer is semicolons (;) at the end of a line suppress output Type more on to keep text from leaving screen too fast diary filename saves a text record of session diary off turns it off Chapter M1: Introduction to MATLAB 10