1. Chp1 MATLAB OverView: Part-1
Engr/Math/Physics 25
Chp1 MATLAB OverView: Part-1
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer

2. Learning Goals Turn On MATLAB and use as a calculator
Create Basic Cartesian Plots
Write and Save simple “Script” Program-files
Execute Conditional Statements
IF, THEN, ELSE, >, <, >=, etc.
Execute Loop Statements
FOR & WHILE

3. MATLAB Environment TWO Interaction Modes INTERACTIVE
Type in the COMMAND WINDOW
Often Called a Command-Window “Session”
Interaction is NOT Saved to Disk
Commands (NOT results) Stored in “Command History” Buffer Window
STORED → Two Types
SCRIPT Files
FUNCTION Files

4. MATLAB Command Window
Typing
Occurs
Here

5. Example Cmd Window Session
>> %Use MATLAB As Calculator
>> 17*19
ans =
323
>> 77/
>> 64^(1/3) + 32^0.2 6
>> (7+11)*2.5
ans = 45
>> L = 14.4
L =
>> W = 13.3
W =
>> Area = L*W
Area =
Time For
Live Demo
Demo left division shown 7\3 = 3/7

6. Script/Function File Editor

7. Script & Function Files (m-files)
SCRIPTS and FUNCTIONS in MATLAB are stored in text files that end with the extension “.m”
These files are called m-files
SCRIPTS (a.k.a. “programs”)
Scripts files are useful for automating tasks that may need to be repeated.
They have no input/output parameters
They can (but probably shouldn’t) share variables with the command workspace

8. Script & Function Files (m-files)
SCRIPTS (cont.)
Scripts are sequences of interactive statements stored in a file
i.e., They look liked Stored versions of Command Window Sessions
FUNCTIONS (a.k.a. “subroutines”)
Function m-files are MATLAB subprograms analogous to FORTRAN Subroutines, or C functions
They communicate with the command window and other functions via a list of INPUT and OUTPUT PARAMETERS or ARGUMENTS

9. Script & Function Files (m-files)
FUNCTIONS (cont.)
Functions COMMUNICATE with the COMMAND WINDOW and other m-files via a list of input and output variables
LOCAL variables are variables defined INSIDE the function
They only can be used inside the function in which they reside.
The number of output parameters used when a function is called must match the number of outputs that the function is expected to return
Good Example from ENGR43 = Rectab.m & MagPh.m

10. Entering Commands & Expressions
MATLAB retains your previous keystrokes.
Use the up-arrow (↑) key to scroll back through the commands.
Press the key (↑) once to see the previous entry, and so on.
Use the down-arrow (↓) key to scroll forward.
Edit a line using the left (←) & right (→) arrow keys the Backspace key, and the Delete key.
Press the Enter key to execute the command

11. Arithmetic Scalar Operations
Symbol
Operation
MATLAB ^
exponentiation: ab
a^b *
multiplication: ab
a*b /
right division: a/b
a/b \
left division: b/a
a\b +
addition: a + b
a + b -
subtraction: a - b
a - b
DEMO: 21/7 = 3 = 7\21
LEFT-Division A\b read from Right-to-Left as: “b divided by A”

12. Math Op Precedence (PEMDAS)
Precedence Operation
First Parentheses, evaluated starting with the innermost pair.
Second Exponentiation, evaluated from left to right.
Third Multiplication and Division with EQUAL precedence, evaluated from left to right.
Fourth Addition and Subtraction with EQUAL precedence, evaluated from left to right.
Demo 19^2/3 is NOT the same as 19^(2/30

13. Precedence Examples >> 8+3*5 ans = 23 >> 8 + (3*5)
>>(8 + 3)*5 55
>> 4^2-12-8/4*2
ans =
>> 4^2-12-8/(4*2) 3 4 1

14. Precedence Examples cont.
>> 3*4^2 + 5
ans = 53
>>(3*4)^2 + 5
149
>>27^(1/3) + 32^0.2
ans = 5
>>27^1/3 + 32^0.2 11 48 3
144 9

15. “=“ → Assignment Operator
Typing x = 3 ASSIGNS the value 3 to the variable x.
We can then type x = x This assigns the value = 5 to x. But in algebra this implies that 0 = 2.
In algebra we can write x+2 = 20, but in MATLAB we cannot.
In MATLAB the LEFT side of the = operator MUST be a SINGLE variable.
The Right side must be a computable value

16. Work Session Commands Command Description clc
Clears the Command window
clear
Removes all variables from memory
clear v1 v2
Removes the variables v1 and v2 from memory
exist(‘var’)
Determines if a file or variable exists having the name ‘var’
quit
Stops MATLAB

17. Work Session Commands cont.1
Description
who
Lists the variables currently in memory
whos
Lists the current variables and sizes, and indicates if they have imaginary parts.
: (Colon)
Generates an array having regularly spaced elements
, (Comma)
Separates elements of an array
; (Semicolon)
Suppresses screen printing; also denotes a new row in an array
… (Ellipsis)
Continues a line

18. whos on First???

19. Special VARS & const’s Command Description ans
Temporary variable containing the most recent answer
eps
Specifies the accuracy of floating point precision
i,j
The imaginary unit (-1)
Inf
Infinity (unbounded magnitude)
NaN
Indicates an undefined numerical result; a.k.a., Not a Number pi
The number pi ( )
DEMO Inf: undef = 37/0 => undef = Inf
NaN returns the IEEE arithmetic representation for Not-a-Number (NaN). These result from operations which have undefined numerical results.
NaN returns the IEEE arithmetic representation for Not-a-Number (NaN). These result from operations which have undefined numerical results;. e.g., try Q = 0/0

20. The Complex Plane
Im (i or j) Re

21. Complex-Number Operations
The number c1 = 1 – 2i is entered as: c1 = 1­2i or c1 = 1-2j
An Asterisk is NOT needed between i or j and a NUMBER, although it is required with a VARIABLE, such as c2 = 5 - i*c1.
Be careful. The expressions
y = 7/2*i and x = 7/2j
give two DIFFERENT results:
y = (7/2)i = 3.5i
and x = 7/(2j) = –3.5j

22. Complex Arithmetic >> Im_Pwr = Z1^3.84 Im_Pwr =
e e+004i
>> e_to_Z = exp(Z2)
e_to_Z =
6.8518e e+007i
>> ln_Z = log(Z1)
ln_Z = i
>> Log_Z = log10(Z2)
Log_Z = i

23. Special VARS & const’s Command Description format short
Four decimal digits (the default);
format long
16 digits;
format short e
Five digits (four decimals) plus exponent; e+03
format long e
16 digits (15 decimals) plus exponent; e–04

24. Discrete Math Funtions
Command
Description
factor(n)
Returns a row vector containing the prime factors of n.
gcd(m,n)
Finds the Greatest Common Divisor/Factor of m & n
lcm(m,n)
Finds the Least Common Multiple for m & n
factorial(n)
Returns the factorial of n; i.e., returns n! = 1*2*3…(n-2)*(n-1)*n
primes(n)
Finds all prime numbers less than n
isprime(n)
Determines if n is a prime number
Demo by: >> isprime(97) ans = 1 * >> isprime(98) ans = 0 >> factor(98) ans = * >> gcf = gcd(51,119) gcf = 17

25. Discrete Math Examples
factor777 = factor(777)
factor777 =
GCF = gcd(1001, 1105)
GCF = 13
F7 = factorial(7)
F7 =
5040
P93 = primes(93)
P93 =
Columns 1 through 12
Columns 13 through 24

26. Arrays An ARRAY is an ORDERED SET of Numbers of with n DIMENSIONS
A regular Number (a SCALAR) is an Array of Dimension ZERO
a VECTOR is a 1-Dim Array
a MATRIX is an ARRAY of Dim  2 with special properties
Graphics from SemaTech site Or

27. Arrays in MATLAB
The numbers 0, 0.1, 0.2, …, 10 can be assigned to the array variable u by typing
u = [0:0.1:10]
To compute w = 5 sin u for u = 0, 0.1, 0.2, 0.3, 0.4,…, 10, the command session is;
>>u = [0:0.1:10];
>>w = 5*sin(u);
The single line, w = 5*sin(u), computed the formula, w = 5 sin(u), 101 times.

28. Array Index >>u(7) ans = 0.6000 >>w(7) 2.8232
Use the LENGTH function to determine how many values are in an array.
>>m = length(w)
m =
101

29. Polynomial Roots MATLAB has a Way-Cool Polynomial Root Finder
Find the roots of x3 − 7x2 + 40x − 34 = 0
>>a = [1,-7,40,-34];
>>roots(a)
ans = i i
1.0000
The roots are x = 1 and x = 3 ± 5i

30. 5th Order Polynomial Find the roots of the 5th Order function
>> roots(r5)
ans = i i i i
1.0000
The roots of g(y)
y1,2 = 3 ± 2j
y3,4 = 1 ± j
y5 = 1

31. Common Math Functions
Fcn
MATLAB ex
exp(x)
sin x
sin(x) √x
sqrt(x)
tan x
tan(x)
ln x
log(x)
cos-1 x
acos(x)
log10 x
log10(x)
sin-1 x
asin(x)
cos x
cos(x)
tan-1 x
atan(x)
Note that MATLAB Trig functions Operate on RADIANS
Convert using Ratio: -rads per 180°
For trig argument in DEGREEs use MATLAB fcns: cosd, sind, tand

32. The “d” Trig Comands for Degrees
>> T1 = sind(77)
T1 =
0.9744
>> T2 = cosd(19)
T2 =
0.9455
>> T3 = tand(53)
T3 =
1.3270
>> T4 = asind(.497)
T4 =
>> T5 = acosd(0.629)
T5 =
>> T6 = atand(1.73)
T6 =

33. Printing From Command Window - 1
Text to Print
Note: MATLAB “Comments” Start with the “%” Sign

34. Printing From Command Window - 2
SELECTText to Print

35. Printing From Command Window - 3
Send to printer from Print Dialog Box
Caveat
In a COMMAND WINDOW session once you Hit Enter () you can NOT Go back to Edit the Text
Can Save your command sequence as an m-file SCRIPT

36. Alternative Cmd Window Printing
Perform MATLAB Operation
Select Desired Text
COPY text to the Windows Paste Buffer
Open Text application
MSWord, WordPad, NotePad, etc.
PASTE the MATLAB Text Into the Text Processor
Print from the Text Processor as Usual

37. DIARY Function to Record Cmnds
Keeping a Session Log → The diary Function
The diary function creates a copy of your session in MATLAB on a disk file, including keyboard input and system responses, but excluding graphics. You can view and edit the resulting text file using any text editor, such as the MATLAB Editor. To create a file on your disk called sept23.out that contains all the functions you enter, as well as output from MATLAB, enter
diary('sept23.out')
To stop recording the session, use
diary('off')
To view the file, run
edit('sept23.out')

38. Command Execution Hierarchy
When you type problem1
MATLAB first checks to see if problem1 is a variable and if so, displays its value.
If not, MATLAB then checks to see if problem1 is one of its own commands, and executes it if it is.
If not, MATLAB then looks in the current directory for a file named problem1.m and executes problem1 if it finds it.
If not, MATLAB then searches the directories in its search path, in order, for problem1.m and then executes it if found.

39. System, Directory, File Cmnds
Command
Description
addpath dirname
Adds the directory dirname to the search path.
cd dirname
Changes the current directory to dirname
dir
Lists all files in the current directory
dir dirname
Lists all the files in the directory dirname
path
Displays the MATLAB search path
pathtool
Starts the Set Path tool
HINT: Consider putting ALL your m-files in ONE Folder/Directory

40. Plotting with MATLAB
Plot over 573°
10 rads = 573 deg

41. MATLAB Plotting Commands
Description
plot(x,y)
Generates a plot of the array y versus the array x on rectilinear axes
title(’text’)
Puts text in a title at the top of the plot
xlabel(’text’)
Adds a text label to the horizontal axis (the abscissa).
ylabel(’text’)
Adds a text label to the vertical axis (the ordinate).
grid
Puts grid lines on the plot
gtext(’text’)
Enables placement of text with the mouse

42. DeskTop Recovery to UnScramble the DeskTop

43. DeskTop “Recovery”

44. Example Problem 1-21 Time For Live Demo Plot This Function Where
T  Temperature (°C)
t  time (minutes)
For: 1  t  3

45. Tutorial on HomeWork Construction Next Time A VERY Important Meeting
All Done for Today
Tutorial on HomeWork Construction Next Time
From 2E: P1.30 Tutorial Next Meeting
A VERY Important Meeting

46. Licensed Electrical & Mechanical Engineer BMayer@ChabotCollege.edu
Engr/Math/Physics 25
Appendix
Bruce Mayer, PE
Licensed Electrical & Mechanical Engineer

47. Example Demo Session >> %Use MATLAB As Calculator >> 17*19
ans =
323
>> 77/
>> 64^(1/3) + 32^0.2 6
>> (7+11)*2.5
ans = 45
>> L = 14.4
L =
>> W = 13.3
W =
>> Area = L*W
Area =

48. Prob 1-21 Command Script From the Command Window
>> T = 6*log(t) - 7*exp(0.2*t);
>> plot(t,T), xlabel('time (min)'),ylabel('Temperature (°C)'), title('Problem 1-21'), grid

49. Prob 1-22 Plot

51. System, Directory, File Cmnds
Command
Description
pwd
Displays the current directory
cd dirname
Changes the current directory to dirname
rmpath dirname
Removes the directory dirname from the search path.
what
Lists the MATLAB-specific files found in the current working directory. Most data files and other non-MATLAB files are not listed. Use dir to get a list of all files
what dirname
Lists the MATLAB-specific files in directory dirname