CMPS 1371 Introduction to Computing for Engineers MatLab

Getting Started In Windows click on the following: Programs Math & Science  MatLab R2008a

Getting Started MATLAB opens to a default window configuration

MATLAB uses a standard windows menu bar To exit MATLAB use the close icon

Command Window Enter commands at the prompt Current Directory MATLAB Windows Command History Workspace Window

MATLAB Windows MATLAB uses several different windows to display data, commands and results. They are not necessarily all open at once

Command Window Similar to a scratch pad Once you hit enter, you can’t edit any commands You can retype them or use the arrow keys to retrieve commands and edit them before hitting enter again Command Window

Command History Records the commands you issue in the command window When you exit the command window, or when you issue the clc command, the command window is cleared But the command history remains Command History

You can transfer commands from the command history to the command window Double click on a command Click and drag

Workspace Window Keeps track of the variables you’ve defined Name Value Class Size Bytes You may need to click on the name bar and select size and bytes in order to see these parameters Workspace Window

When you define variables in the command window, they are listed in the workspace window

Current Directory The current directory window is a list of files When you try to load information from a file or try to save information – MATLAB uses the current directory

Document Window If you double click on any variable in the workspace window MATLAB launches a document window containing the array editor You can edit variables in the array editor

Document Window

Figure Window When Figures are created a new window opens It’s extremely easy to create graphs in MATLAB

The semicolon suppresses the output from each command

Editing Window This window allows you to type and save a series of commands without executing them There are several ways to open an editing window From the file menu With the new file icon

Open an editing window from the file menu or with the new file icon

Save and Run Write your code in the editing window, then run it using the Save and Run icon

Solving Problems We’ve already solved some simple problems We need to understand how MATLAB works to solve more complicated problems

Variables MATLAB allows you to assign a value to a variable A=3 Should be read as A is assigned a value of 3 Use the variables in subsequent calculations

Naming Variables All names must start with a letter They may contain letters, numbers and the underscore ( _ ) Names are case sensitive There are certain keywords you can’t use

Keywords Use the iskeyword function for a list of keywords >>iskeyword ans = 'break' 'case' 'catch' 'continue' 'else' 'elseif' 'end' 'for' 'function' 'global' 'if' 'otherwise' 'persistent' 'return' 'switch' 'try' 'while'

Which of these names are allowed in MATLAB? test Test if my-book my_book Thisisoneverylongnamebutisitstillallowed? 1stgroup group_one zzaAbc z34wAwy?12# sin log x x x x x x bad idea

Scalar Calculations You can use MATLAB like you’d use a calculator >> ans=19 Command Prompt Result

Assignment Operator To define a variable a we might type a=1+2 which should be read as: “a” is assigned a value of 1+2

Order of Operation Same as you’ve learned in math class Same as your calculator Parentheses first Exponentiation Multiplication / division Addition / subtraction

Order of Operation 5*(3+6)= 45 5*3+6= 21 White space does not matter!!! 5*3 + 6= 21

Parentheses Use only ( ) { } and [ ] mean something different MATLAB does not assume operators 5 * (3+4) not 5(3+4)

Compute from left to right 5*6/6*5= 25 5*6/(6*5)= 1

Here’s an example Find the surface area of a cylinder r = radius r = 5 h = height h = 10 π r 2 2π r * h

Try some Type each expression on the command line and then press Enter >> / 2 >> (7 + 8) / 2 >> 5 ^ 3 / 2 >> sqrt(64) >> x = 15 >> x = 3 * x – 12 >> y = pi >> z = y * 2 >> A = 12; >> B = 4; >> C = A / B + A – B * 2; >> C