Introduction to Computing using Matlab

sind(x

sine (xin degrees)

sin(x)

sine (xin radians)

sqrt(x)

square root

i

square root of (-1)

tand(x)

tangent (xin degrees)

tan(x)

tangent (xin radians)

eps

the smallest difference betweenany two numbers in MATLAB

ans

the value of the last expression that was not assigned to a variable

factorial(x)

x!

Comment lines

•Lines that start with percent sign (%) •Common for first few lines to be commentsand to briefly explain what commands in file do •Editor Window shows comment lines in green

floor(x)

round toward minus infinity

fix(x)

round toward zero

coth(x)

(e^x+e^-x)/(e^x-e^-x)

cosh(x)

(e^x+e^-x)/2

tanh(x)

(e^x-e^-x)/(e^x+e^-x)

sinh(x)

(e^x-e^-x)/2

Can read the variable

(get its value)

j

(same as i) but commonly used instead of i in electrical engineering

Can write to the variable

(set its value)

A function's arguments can be

-Numbers -Variables (explained in next section -Expressions involving numbers, variables, orfunctions

A script file is a sequence of MATLAB commands, also called a program

-When a script file runs (is executed),MATLAB performs the commands in the order they are written, just as if they were typed in the Command Window -When a script file has a command that generates an output (e.g. assignment of a value to a variable without semicolon at the end), the file displays the output in the Command Window

Right division

/

A variable name cannot contain a space.Two common alternatives:

1. Use an underscore in place of a space, e.g., speed_of_light 2. Capitalize the first letter of all but first word, e.g.,speed_Of_Light (This is known as camel case!)

pi

3.14

To change the value of a variable, just assign it the new value

>> ABB=72; >> ABB=9; >> ABB ABB = 9

To change the value of a variable, just assign it the new value

>> ABB=72; >> ABB=9; >> ABBABB =9

Can do multiple assignments on one line by separating with a comma or semicolon. If semicolon, no display for that assignment

>> a=12, B=4; C=(a-B)+40-a/B*10 a = 12 C = 18

A variable must have a value before you use it in an expression

>> x = 3; >> x+2ans=5 >> x + y% assume y undefined??? Undefined function orvariable 'y'

To find out the value of a variable, just type it and press ENTER

>> x = 3; >> y = 10 * x; >> z = y ^ 2; >> yy =30 >> zz =900

You must define a variable (give it a value) before you can use it in an argument of a function

>>sqrt( x )% assume x undefined ??? Undefined function or variable 'x' >> x = 144; >>sqrt( x ) x = 12

Fourth

Addition and subtraction.

A keyword is a word that has special meaning to MATLAB

Appear in blue when typed in the Editor Window Can't be used as variable names

clc command

Clears Command Window display -Up and down arrows still bring back previous commands

Figure Window

Contains output from graphic commands.

Editor Window

Creates and debugs script and function files.

who

Displays a list of the variables currently in memory

whos

Displays a list of the variables currently in memory and their size, together with information about their bytes and class

Second

Exponentiation.

Can type several commands in same line by putting a commabetween commands

Hard to read, so don't do this often

A function

Has a name -Can have zero or morearguments(inputs) -Can produce zero or more outputs

Command History Window

Logs commands entered in theCommand Window.

Command Window

Main window, enters variables,runs programs.

Third

Multiplication, division (equal precedence).

First

Parentheses. For nested parentheses, the innermost are executed first.

Help Window

Provides help information.

Workspace Window

Provides information about thevariables that are stored.

clear

Removes all variables from memory

Command History Window

Shows previous commands, including ones from previousMATLAB sessions -Double-clicking on command puts it in Command Window andexecutes it -Can drag command to Command Window, make changes incommand, then execute it -To clear one or more commands, select the lines to delete, rightclick, choose Delete Selection -To clear entire history, right click, select Clear Command History

Current Folder Window

Shows the files in the current folder.

Percent sign(%)

When typed at beginning of line, MATLAB treats line as acommentand doesn't execute line

Semicolon (;)

When typed at end of command, suppresses output. (Only prompt displayed at next line) -Useful for preventing display of large outputs

Left division

\

abs(x)

absolute value

(xin radians)

asin(x),acos(x),atan(x),acot(x)

(xin degrees)

asind(x),acosd(x),atand(x),acotd(x)

MATLAB is

case-sensitive

cosd(x)

cosine (xin degrees)

cos(x)

cosine (xin radians)

cotd(x)

cotangent (xin degrees)

cot(x)

cotangent (xin radians)

exp(x)

e^x

inf or Inf

infinity

log10(x)

log base 10

NaN

nan not-a-number. Used to express mathematically undefined values, such as 0/0

log(x)

natural log (base e)

nthroot(x,n)

nth real root

rem(x,y)

remainder after x is divided by y (also called modulus)

clear x y z

removes only variables x, y, and z from memory

sign(x)

returns the sign of input x as -1, 0, or 1 (negative, zero, or positive respectively)

round(x)

round to nearest integer

ceil(x)

round toward infinity

A variable name

•Must begin with a letter •Can be up to 63 characters long •Can contain letters, digits, and underscores (_) •Can't contain punctuation, e.g., period,comma, semicolon Avoid using the name of a built-infunction as the name of a variable, e.g.,don't call a variableexporsqrt

NOTES ABOUT SCRIPT FILES

•Using a script file is convenient because it canbe edited (corrected and/or changed) andexecuted many times •Script files can be typed and edited in any texteditor and then pasted into the MATLAB editor •Script files are also calledM-filesbecause the extension.m is used when they are saved