CPET190_Lect8

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October 3, 2005 Lecture 8 - By Paul Lin 1

CPET 190

Lecture 8

Problem Solving with MATLAB

http://www.etcs.ipfw.edu/~lin

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Lecture 8: MATLAB Program Design

and Flow Control

8-1 Top-Down Program Design

Techniques

8-2 Algorithm and Pseudocode8-3 Data Types

8-5 Relational and Logical Operators

8-5 Logical Functions

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Review: MATLAB sequential programs

Sequential Program Step 1- Read user input

Step 2 - Process thedesired tasks toproduce the answer

Step 3 - Display or plotthe answer

Step 4 - Quit or end theprogram

Sequence statements in a

program are executed oneafter the other in the orderin which they are written

Add grade to total

Add 1 to counter

Sequence Flowchart

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8-1 Top-Down Program Design

Technique

A formal design process Top-down

Divide and Conquer: divide the large andcomplex task into smaller ones

Steps (with some refinements if needed)

1. Clearly state the problem

2. Planning the program (define inputs andoutputs)

3. Design the algorithm and data structures

4. Coding (Translate algorithm into MATLABstatements)

5. Test the MATLAB program

6. Document the program and the result

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8-2 Algorithm and Pseudocode

Algorithm A procedure for solving a problem in terms of

the actions to be executed, and the order in

which these actions are to be executed

Pseudocode definition: An artificial and informal language that helps

programmers develop algorithm

An intermediate step that helps a programmer

to translate the English-language description ofproblem in to a computer program

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8-2 Algorithm and Pseudocode

An example of Psedocode for algorithm

1. Prompt user to enter temperature in

degrees Fahrenheit

2. Read the temperature (temp_f)3. Convert to temp_k in kelvin: temp_k

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8-3 MATLAB Data Types

15 Fundamental Data Types in MATLAB Logical, Char, Numeric (int8, uint8, int16,

uint16, int32, uint32, int64, uint64), Single,

Double, Cell, Structure (user classes), Java

classes, Function handle

All in the form of array

Minimum size of 0-by-0 (scalar)

2-dimensional version of these arrays arecalled matrices

N-dimensional of any size

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8-3 MATLAB Data Types (continue)

Logical Data Type Two Values (True or False)

NonZeroTrue (1)

ZeroFalse (0)

Produced by two functions>> a = true

a = 1

>> b = false

b = 0 Logical and Relational operators can also

produce true or false

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8-4 Relational Operators

Relational Operators making quantitativecomparisons

Symbols

== Equal~= Not equal

< Less than

> Greater than

= Greater than or equal

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8-4 Relational Operators (continue)

Some Relational Operator Examples

>> 2 < 3

ans = 1

>> 3 < 2

ans = 0>> 3 == 3

ans = 1

>> 2 > 4 >= 3

ans = 1

>> 'A' > 'B'

ans = 0

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8-4 Relational Operators (continue)

Some More Examples

>> A = fix(rand(3)*10)

A =

8 6 6

5 8 32 0 8

>> B = fix(rand(3)*10)

B =

5 3 6

7 1 3

4 1 5

>> A == B

ans =

0 0 1

0 0 10 0 0

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October 3, 2005Lecture 8 - By Paul Lin

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8-4 Logical Operators

Three Types of Logical Operators and Functions Element-Wiseoperate on logical arrays

& for AND

| for OR

~ for NOT

xor for Exclusive OR

Short-Circuitoperate on scalar, logicalexpressions

Bit-Wiseoperate on bits of integer values orarrays

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October 3, 2005Lecture 8 - By Paul Lin

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8-4 Logical Operators (continue)

Example: Element-wise>> A = [1 0 1 1]

>> B = [0 1 0 1]

>> A & B

ans = 0 0 0 1

>> A | B

ans = 1 1 1 1

>> xor(A,B)

ans = 1 1 1 0

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8-4 Logical Operators (continue)

Logical Operators for evaluating logicalexpressions (scalar value)

Short-circuit logical AND &&

Short-circuit logical OR ||

Syntax

A && B

A || B

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8-4 Relational and Logical Operators

Example: a statement that avoids divide-by-zeroerrors when b equals zero:

>> a = input(Enter a = )

>> b = input(Enter b = )

>> x = (b ~= 0) && (a/b > 18.5)Case 1: b = 1, a = 20, x = true && true = 1

Case 2: b = 1, a = 10, x = true && false = 0

Case 3: b = 0, a = 20, x = false && Not-evaluated

= 0

Case 4: b = 0, a = 10, x = false = 0

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Logical Functions and - Element-wise logical AND ( & )

or - Element-wise logical OR ( | )

not - Logical NOT (~)

xor - Logical EXCLUSIVE OR

any - True if any element of vector isnonzero

all - True if all elements of vector arenonzero

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Example: Using functions and, or, not

A = [0 1 1 0 1]; B = [1 1 0 0 1];

A & B

and(A, B)

asn = 01001

A | B

or(A, B)

ans = 11101

~A

not(A)

ans = 10010

xor - Returns 1 for every

element location that is

true (nonzero) in only onearray, and 0 for all other

elements

xor(A,B)

ans =10100

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Truth Table for xor

A B xor(A,B)

Zero Zero 0

Zero NonZero 1

NonZero Zero 1NonZero NonZero 0

Example: Given

A = [0 0 pi eps] and

B = [0 -2.4 0 1], then

C = xor(A, B)

C =

0 1 1 0

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More Logical Functions logical(n) convert numerical value to logical

values; true for Non-zero, false for Zero

ischar(n) returns true if n is a char. array

isempty(n) - returns true if n is an empty array isinf(n) returns true if n is infinite (Inf)

isnan(n) returns true if n is NaN (not anumber

isnumeric(n) returns true if n is a numericarray

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Summary

Top-down program design techniques Algorithm and pseudocode

Data types

Relational and logical operators

Logical functions

Next:

Control Flow Loop Control

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Question?

Answers

Email: [email protected]

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