Chapter 1.pdf

INTRODUCTION TO MATLAB
NED University of Engineering & Technology

• Credit Hours: 2 + 1
• Course Learning Outcomes (CLOs):
Course Details
S.
No.
CLOs Taxonomy PLOs
Assessment
Tools
1
Understand and identify the fundamental
concepts of computer programming
C1 1
Test /Mid/
Final
2
Apply the acquired knowledge to
mechanical engineering problems
C3 2
Test /Mid/
Final
3
Practice the numerical analysis and
optimization on programming language
P3 5
Sessional
+Final
Practicals
4
For given Mechanical engineering
problems, execute the regression models
and make comparison of the predicted
and measured data
P4 3
Sessional
Practical

• Different windows in MATLAB
• Arithmetic operations with scalars using MATLAB.
• Scalar variables and their use in arithmetic
calculations
• Elementary Math built-in functions
• Script files → how to write, save, and execute
simple MATLAB programs
Outline
Textbook: A. Gilat, Matlab: An Introduction with Applications 4th Edition. John Wiley
& Sons, Incorporated, 2017. (Chapter 1: Introduction)

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Prerequisites for solving a problem using MATLAB
• Mathematics
• An algorithm
• The exact rules for writing MATLAB statements
• Correct usage of MATLAB utilities
• Converting algorithm into MATLAB statements
and/or program

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Default view of MATLAB desktop
COMMAND WINDOW
WORKSPACE
WINDOW
COMMAND HISTORY
WINDOW
CURRENT
FOLDER
WINDOW

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Default view: Home → Layout → Default

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• Main window: For executing commands
• Command line: The line with command prompt >>
Command Window: Executing commands one at a time
Command 1:A=5
press enter
Command 2: B=10
press enter
Command 3: C=A+B
press enter
To execute
each
command:
Press Enter
The cursor next to the command
prompt is prompting the user to enter
the next Command

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Command Window: Executing several commands
3 commands in the same
line separated by a
comma
Order of
execution:
Left to Right

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Command Window: Editing
• Editing:
The already executed command can not be corrected
and re-executed

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Command Window: Editing
Command-line editing:
• Left-arrow, Right-arrow
• Up-arrow and Down-arrow for accessing history
• Smart recall: type some character and press
Up-arrow and Down-arrow

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Command Window: Use of percent symbol (%)
Comment
Comment line is not executed when ENTER is
pressed
Comments are added to aid the programmer for his/her reference

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Command Window: Use of Semi-colon (;)
Output of the command is displayed
Output of the command
is not displayed

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Command Window: Use of Semi-colon (;)

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Command Window: Use of the command clc
clc → clears the command window only
CAUTION: The commands are CASE-SENSITIVE!

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Drawbacks of a command window
• The commands in the Command window
cannot be saved and executed again.
• It is not interactive.
• Already executed command can not be
modified
• Better option: script file

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Command Window: Font size: Home → Preferences → Fonts

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Useful commands you should know
CAUTION: The commands are CASE-SENSITIVE!
• help → lists all the primary help topics.
• help <command> → displays information about the command.
• doc On-line help → accesses the hypertext reference manual.
for this
• doc <command> → displays information about the command.
• type <command> → Displays the actual MATLAB code
command.
• lookfor <keyword> → Searches all MATLAB commands for this
keyword.

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ATTENTION: The commands are CASE-SENSITIVE!
• who → Lists all the current variables.
• whos → Lists all the current variables in more detail than who.
• save → Saves all of your variables.
• ^C → Abort the command which is currently executing (i.e., hold down
the control key and type c).

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ATTENTION: The commands are CASE-SENSITIVE!
• clc → clears the command window (but does not clear the saved
variables in the workspace)
• clear all → deletes all the saved variables from the workspace (but
does not clear the command window) and brings the cursor at top
• clear variable → deletes only that particular variable from the
workspace
• date → gives current date
• calendar→ shows up the calendar of the ongoing month

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Busy…

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Command History
• The Command History Window → includes commands from previous
sessions.
• A command in the Command History Window can be used again in the
Command Window.
• By double-clicking on the command, the command is reentered in the
Command Window and executed.
• It is also possible to drag the command to the Command Window, make
changes if needed, and then execute it.
• Clearing Command history:
• Whole history
• A selection

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Simple Arithmetic Operations With Scalars
Addition: 3+2
Subtraction: 3-2
Multiplication: 3*2
Division: 3/2 or 23
Exponent: 3^2

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Order of Precedence

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Order of Precedence: Practice

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Display formats
Command Description Example
format short
(default)
upto 4 decimal digits
>> 290/7
ans =
41.4286
format long upto 15 decimal digits
>> 290/7
ans =
41.4285714285
71431
format short e scientific notation with 4 decimal digits
>> 290/7
ans =
4.1429e+001
format long e scientific notation with 15 decimal digits
>> 290/7
ans =
4.14285714285
7143e+001

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Example
Display formats
Command Description
format short g 5 s.g.f of floating digits
>> 290/7
ans =
41.429
format long g 15 s.g.f of floating digits
>> 290/7
ans =
41.4285714285
714
format bank upto 2 decimal digits
>> 290/7
ans =
41.43
format loose
(default)
Adds empty lines (opposite of compact).
format compact
Eliminates empty lines to allow more lines with information
displayed on the screen.

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Display formats: compact vs loose

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Inf & NaN
1/0
Infinity:
inf + 3
Not-a-Number (NaN):
0/0

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Variables: Storing data
Save value in a variable:
x = 3
x = 4 (over-ridden)
Variables are case-sensitive:
T = 2
t = 3
Z = t+T;
Assignment
operator
=

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Variables: Naming rules
1. May consist of:
✓ letters A-Z, a-z
✓ digits 0-9
✓ underscore ( _ )
2. Must start with a letter.
3. Variable names are case-sensitive
4. Can be up to 63 characters long
5. Avoid using the built-in functions as the variable
name e.g. cos, sin, sqrt etc.

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Variables: Predefined keywords that can not be used as
variable name
for
function
global
if
otherwise
parfor
persistent
break
case
catch
classdef
continue
else
elseif
end
return
spmd
switch
try
while

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Variables: Predefined variables
ans
pi
…

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a = sqrt(4)
Elementary math built-in functions
A function has a name and an argument in parentheses.
a = 4

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Elementary functions in MATLAB: Trigonometry
Function Description Example
sin(x)
sind(x)
Sine of angle x (x in radians).
Sine of angle x (x in degrees).
>> sin(pi/6)
ans =
0.5
cos(x)
cosd(x)
Cosine of angle x (x in radians).
Cosine of angle x (x in degrees).
>> cosd(30)
ans =
0.86603
tan(x)
tand(x)
Tangent of angle x (x in radians).
Tangent of angle x (x in degrees).
>> tan(pi/6)
ans =
0.57735
cot(x)
cotd(x)
Cotangent of angle x (x in radians).
Cotangent of angle x (x in degrees).
>> cotd(30)
ans =
1.7321

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Elementary functions in MATLAB: Trigonometry
• Inverse trigonometric functions are:
asin(x), acos(x), atan(x), acot(x) for the angle in
radians.
asind(x), acosd(x), atand(x),acotd(x) for the angle
in degrees.
•Hyperbolic trigonometric functions are
sinh(x), cosh(x), tanh(x), and coth(x).

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Elementary functions in MATLAB: Exponential
sqrt(x) square root
>> sqrt(81)
ans =
9
nthroot(x,n) Real nth root of a real number x.
>> nthroot(80,5)
ans =
2.4022
exp(x) Exponential ex
>> exp(5)
ans =
148.41
3
log(x) Natural logarithm.
>> log(1000)
ans =
Base e logarithm (ln). 6.9078
log10(x) Base 10 logarithm.
>> log10(1000)
ans =

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Elementary functions in MATLAB: Rounding & Remainder
round(x) Rounds to the nearest integer.
>>
round(3/2)
ans =
2
fix(x) Rounds towards zero.
>> fix(3/2)
ans =
1
ceil(x) Rounds towards +ve infinity.
>>
ceil(3/2)
ans =
2
floor(x) Rounds towards -ve infinity.
>>
floor(3/2)
ans =
1
rem(x,y) Returns the remainder after x is divided by y.
>>
rem(35,3)
ans =
2
sign(x) Signum function. Returns 1 if x > 0, -1 if x < -1 & 0 if x =0
>> sign(5)
ans =
1

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Practice …..
fix and rem
Converting 40 inches to feet-inch.
feet = fix(40/12)
inches = rem(40, 12)

Chapter 1.pdf

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