CPET 190

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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 Pseudocode
• 8-3 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 the desired tasks to produce the
  answer
• Step 3 - Display or plot the answer
• Step 4 - Quit or end the program
• Sequence statements in a program are executed one
  after the other in the order in which they are
  written

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 and complex
  task into smaller ones
• Steps (with some refinements if needed)
• Clearly state the problem
• Planning the program (define inputs and outputs)
• Design the algorithm and data structures
• Coding (Translate algorithm into MATLAB
  statements)
• Test the MATLAB program
• 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 of
  problem in to a computer program

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8-2 Algorithm and Pseudocode

• An example of Psedocode for algorithm
• Prompt user to enter temperature in degrees
  Fahrenheit
• Read the temperature (temp_f)
• Convert to temp_k in kelvin temp_k lt- (temp_f
  32) 273.15
• Write (display) temperature in kelvins

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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 are called
  matrices
• N-dimensional of any size

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8-3 MATLAB Data Types (continue)

• Logical Data Type
• Two Values (True or False)
• NonZero True (1)
• Zero False (0)
• Produced by two functions
• gtgt a true
• a 1
• gtgt 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 quantitative
  comparisons
• Symbols
• Equal
• Not equal
• lt Less than
• gt Greater than
• lt Less than or equal
• gt Greater than or equal

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8-4 Relational Operators (continue)

• Some Relational Operator Examples
• gtgt 2 lt 3
• ans 1
• gtgt 3 lt 2
• ans 0
• gtgt 3 3
• ans 1
• gtgt 2 lt 3
• ans 1
• gtgt 4 gt 3
• ans 1
• gtgt 'A' gt 'B'
• ans 0

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8-4 Relational Operators (continue)

• Some More Examples
• gtgt A fix(rand(3)10)
• A
• 8 6 6
• 5 8 3
• 2 0 8
• gtgt B fix(rand(3)10)
• B
• 5 3 6
• 7 1 3
• 4 1 5

gtgt A B ans 0 0 1 0 0
1 0 0 0
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8-4 Logical Operators

• Three Types of Logical Operators and Functions
• Element-Wise operate on logical arrays
• for AND
• for OR
• for NOT
• xor for Exclusive OR
• Short-Circuit operate on scalar, logical
  expressions
• Bit-Wise operate on bits of integer values or
  arrays

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8-4 Logical Operators (continue)

• Example Element-wise
• gtgt A 1 0 1 1
• gtgt B 0 1 0 1
• gtgt A B
• ans 0 0 0 1
• gtgt A B
• ans 1 1 1 1
• gtgt xor(A,B)
• ans 1 1 1 0

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8-4 Logical Operators (continue)

• Logical Operators for evaluating logical
  expressions (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-zero
  errors when b equals zero
• gtgt a input(Enter a )
• gtgt b input(Enter b )
• gtgt x (b 0) (a/b gt 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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8-5 Logical Functions

• 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 is nonzero
• all - True if all elements of vector are nonzero

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8-5 Logical Functions

• 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 one array, and 0 for
all other elements xor(A,B) ans 10100
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8-5 Logical Functions

• Truth Table for xor
• A B xor(A,B)
• Zero Zero 0
• Zero NonZero 1
• NonZero Zero 1
• NonZero 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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8-5 Logical Functions

• 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 a number
• isnumeric(n) returns true if n is a numeric
  array

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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 lin_at_ipfw.edu