EGR 115 Introduction to Computing for Engineers Introduction to MATLAB Friday 29 August 2014 EGR 115 Introduction to Computing for Engineers

EGR 115 Introduction to Computing for Engineers

Introduction to MATLAB

Friday 29 August 2014 EGR 115 Introduction to Computing for Engineers

http://www.erau.edu/

Lecture Outline


• Introduction to MATLAB The MATLAB Environment Using MATLAB as a Calculator

Slide 2 of 13


Introduction to MATLABThe MATLAB Environment


Workspace:• Currently defined

variables

Command Window:• Main interface

Command History:• Prior commands

Current Directory:• A list of files & folders

Help Browser:• Help on a variety of

topics

Slide 3 of 13


Introduction to MATLABThe MATLAB Environment


• Compute the area of a circle: is a predefined variable “pi”

Assignment with semicolon suppressed output!!

Assignment without semicolon output not supressed!!

Command History:• Prior commands

Slide 4 of 13


Introduction to MATLABThe MATLAB Environment – Saving to *.m files


• Saving commands to a file for reuse – “.m” files Select “New Script” ( )

Run Icon:• Select to run code

- Be sure to save files onto the “p:” drive.- Organization is very important!!!

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Introduction to MATLABThe MATLAB Environment – How to get “help”


• If you know what you are looking for>> help sqrt

• If you not exactly sure what you are looking for>> lookfor sqr

• Can use the “Tab” key to autocomplete

>> sqr

• Use the Help radio button (or >> doc sqrt)Slide 6 of 13


Introduction to MATLABThe MATLAB Env – Some important commands


• Stop the currently executing task>> Ctrl + C

• To clear the command window>> clc

• Remove variables from workspace>> clear all

Slide 7 of 13


Introduction to MATLABUsing MATLAB as a Calculator


• Some basic operations +, -, *, /, (add, subtract, multiply, devide) and ^ exponential (i.e., 2^3 is ) Use parentheses liberally (e.g., 2 * 3 + 4 vs 2 * (3 + 4)) Use % to precede any comments (comment profusely)

• Precedence of operatorsPrecedence OperationFirst Parentheses (innermost first)Second Exponentiation (from left to right)Third Multiplication and division (equal precedence, from left to right)Fourth Addition and subtraction (equal precedence, from left to right.)

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• Which of the following is the correct result?

MATLAB Expression Result #1 Result #2

>> 8 + 3 * 5 23 55

>> (8 + 3) * 5 23 55

>> 8 / 4 * 2 1 4

>> 8 / (4 * 2) 1 4

>> 3 * 4 ^ 2 + 5 53 149

>> 27 ^ 1 / 3 9 3

>> 27 ^ (1 / 3) 9 3

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Introduction to MATLABValid Variable Names


• Valid Names for MATLAB Variables MUST begin with a letter (a-z or A-Z). Followed by any combination of letters, numbers (0-9), and

the underscore (_) characters. o CHARACTERS such as &,^,%,@,… are not allowed

MATLAB keywords cannot be variables (e.g., for, if, end,…)o For a complete list, run the “iskeyword” command.o Valid variable names: “Area_51” , “x0”, o Invalid variable names: “_Area_51”, “0x”, “end”, “n!”,

MATLAB variables are case-sensitiveo Cost, cost and coSt are all different variable names

Use meaningful variable names!!Slide 10 of 13




• In-Class Problem: From our physics classes, we know that the displacement ()

of an object, at time t, can be described as:

Given: = 10 m, = 15 m/s, and = -9.8 m/sec2, calculate the displacement at time = 5 sec.

20 0 0

1

2x x v t a t

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Introduction to MATLABUsing MATLAB as a Calculator - Graphing Calculator


• Simple Example: Plot s vs Generate an array of the discrete values of the independent

variable (i.e., )o Say, goes from 0 to 10 seconds in steps of 0.1 seconds>> t = 0:0.1:10;>> plot(t, sin(t));

0 1 2 3 4 5 6 7 8 9 10-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

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Next Lecture


• MATLAB basics Variables and arrays

Slide 13 of 13


Documents

EGR 115 Introduction to Computing for Engineers Introduction to MATLAB Friday 29 August 2014 EGR 115 Introduction to Computing for Engineers