Branching Looping3

8/3/2019 Branching Looping3

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Branching and Looping Statements

charturong.ee.engr.tu.ac.th/CN208

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Introduction

MATLAB MATLAB 2 branches (code) loops

top-down design techniques

(logical data type)

branches loops


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top-down design

top-down design

(input) (output)

(design the algorithm) MATLAB


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(pseudocode)

pseudocode pseudocode MATLAB MATLAB

Pseudocode MATLAB


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1: Temperature Conversion

MATLAB


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top-down design

pseudocode Prompt user to enter temperature in degree Fahrenheit

Read temperature in degrees Fahrenheit (temp_f)

temp_c in Celsius (temp_f 32) / 1.8

Write temperature in Celsius

? A( ) ( ) 32 /1.8T in Celsius T in Fahrenheit!


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temp_conversion.m

% Script file: temp_conversion

% Programmer: .

% Purpose: to convert an input temperature from degrees Fahrenheit

% to an output temperature in Celsius.

% Define variables:

% temp_f -- Temperature in degrees Fahrenheit

% temp_c -- Temperature in degrees Celsius

% Prompt the user for the input temperature

temp_f = input('Enter the temperature in degrees Fahrenheit:');

% Convert to Celsius.

temp_c = (temp_f - 32) / 1.8;

% Write out the result.

fprintf('%6.2f degrees Fahrenheit = %6.2f Celsius.\n', temp_f, temp_c);


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Testing the program


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The Logical Data Type

MATLAB (logical data type) 2 (true) (false) MATLAB 6.5 2 relational operators logicoperators

logical >> a1 = true;

true 1 false 0 0 true 0 false


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Relational Operators

Relational ==

~=

=


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relational operators

3 < 4

3 == 4

3 ~= 4

3 4 +10

3^2 >= 4

(1) (0)

(1) (1) (0) (1)


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Logic Operators

logic relational (true)

(false)logic MATLAB 3

logic &

|

~

(AND) (OR)

(NOT)


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logic

>> x = (5 > 3) & (2 < 9);

x (true)

(AND) (OR) (NOT)P Q

false false

false true

true false

true true

P & Q P | Q ~P

false false true

false true

false true false

true true


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Branches

MATLAB

if switch

if

if

if expression

(command 1)(command 2)

end

MATLAB commands if end


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if else if

else

if expression

(commands evaluated if expression is true)

else

(commands evaluated if expression is false)

end

expression MATLAB commands ( 1 ) if else expression commands else end


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elseif

if elseif

if expression_1

(commands_1 evaluated ifexpression_1 is true)

elseif expression_2


elseif expression_3


else

(commands evaluated if no other expression is true)

end

expression_1 commands_1 ( 1 ) end expression_1 expression_2

: else commands else


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2: function of two variables

MATLAB f(x,y) x y f(x,y) f(x,y)

f(x,y) = x + y, x >= 0 and y >= 0x + y2, x >= 0 and y < 0

x2 + y, x < 0 and y >= 0

x2 + y2, x < 0 and y < 0


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pseudocode Prompt the user for the values x and y

Read x and y

ifx >= 0 and y >= 0

func

x + yelseifx >= 0 and y < 0

func x + y^2

elseifx < 0 and y >= 0

func x^2 + y

else

func x^2 + y^2

end

Write out f(x,y)


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func_xy.m

% Script file: func_xy.m

% Programmer: ...................

% Purpose: This program solves the function f(x,y) for a user-

% specified x and y, where f(x, y) is defined as:

% f(x,y) = x + y, x >= 0 and y >= 0

% x + y2, x >= 0 and y < 0

% x2 + y, x < 0 and y >= 0

% x2 + y2, x < 0 and y < 0

%

% Define variables:

% x -- first independent variable

% y -- second independent variable% func -- resulting function


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% Prompt the user for the values x and y

x = input('Enter the x coefficient: ');

y = input('Enter the y coefficient: ');

% Calculate the function f(x,y)

if x >= 0 & y >= 0

func = x + y;

elseifx >= 0 & y < 0

func = x + y^2;

elseifx < 0 & y >= 0

func = x^2 + y;

else

func = x^2 + y^2;

end

%Write the value of the function

disp (['The value of the function is ', num2str(func)]);


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switch switch branching

switch switch switch_varcase case_expression_1

(commands_1)

case case_expression_2

(commands_2)otherwise

(commands_3)

end

switch_var

case_expression_1

commands_1

( 1 ) end switch_varcase_expression_2 commands_2 case otherwise

: otherwise


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case switch case case case

(brackets)

switch switch_var

case {case_expression_1, case_expression_2}

(commands_1)case {case_expression_3, case_expression_4}

(commands_2)

otherwise

(commands_3)

end

switch_var (double) (character string)


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switch 1

10 switchvalue = input('Choose a integer between 1 and 10: ');

switch value

case {1, 3, 5, 7, 9}

disp('The number is odd.');

case {2, 4, 6, 8, 10}

disp('The number is even.');

otherwise

disp('The number is out of range.');end


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switch char switch

(character string) x

x = 2.7;

units = 'm' ;

switch unitscase {'inch' , 'in' }

y = x/2.54;

case {'feet' , 'ft' }

y = x/2.54/12;

case {'meter' , 'm' }y = x/100;

otherwise

disp(['Unknown Units: ', units])

y = nan;

end


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2 for while

2 while expression for


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while

while expression expression while expression MATLAB end

while

while expression

(commands)

end


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while

while loop

sum = input('What is five plus ten?: ');

while (sum ~= 15)

disp('Nope! Your answer is incorrect.');

sum = input('What is five plus ten?: ');

end

disp('Great! You are smart.')


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for

for ( 1 ) expression end expression

forindex = array

(commands)end

index (loop variable) array (loop control expression) array index commands array first:incr:last


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for

sum = 0;forii = 1:10

sum = sum + ii;

fprintf('sum = %6.2f.\n', sum);

endfprintf('The value of ii is now %d.\n', ii);


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for1. for MATLAB array

row vector 1 102. 1 ii 1

array for end sum =sum + ii 0 + 1

13. fprintf end

for array ii 2 ii = 2 sum = sum + ii = 1 +2 3

4. MATLAB 3 array ii commands for end


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2 for

sum = 0;forii = 1:2:9

sum = sum + 1;

fprintf('sum = %6.2f.\n', sum);

endfprintf('The value of ii is now %d.\n', ii);


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for

indexcommands for index for

for bug

sum = 0;

forii = 1:10

ii = 5;

sum = sum + ii;

fprintf('sum = %6.2f.\n', sum);end

fprintf('The value of ii is now %d.\n', ii);

for 10 sum

50


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break continue

2

while for break continuebreak for while

MATLAB end

continue

for

while

MATLAB


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breakforii = 1:5

ifii == 3 break;end

fprintf('ii = %d\n', ii);

end

disp(['End of loop!']);

m-file run ii = 1

ii = 2

End of loop! ii 3 if

break for end


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continueforii = 1:5

ifii == 3

continue;end

fprintf('ii = %d\n', ii);

end

disp(['End of loop!']);

m-file run ii = 1

ii = 2

ii = 4

ii = 5

End of loop!

ii 3 ifcontinue for ii 4


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Nested Loops

2 nested loops for

for (two nested for loops)

forii = 1:3

forjj = 1:3

product = ii * jj;

fprintf('%d * %d = %d\n', ii, jj, product);

end

end


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for() 1 ii for() 3 jj

1, 2, 3 for

for ii 2 for for ii 3

1 * 1 = 11 * 2 = 2

1 * 3 = 3

2 * 1 = 2

2 * 2 = 4

2 * 3 = 6

3 * 1 = 3

3 * 2 = 6

3 * 3 = 9


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break continue nested loopsbreak continue

break continue forii = 1:3

forjj = 1:3

ifjj == 3break;

end

product = ii * jj;

fprintf('%d * %d = %d\n', ii, jj, product);

end

fprintf('End of inner loop\n');

end

fprintf('End of outer loop\n');


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jj 3 break End of inner loop ii 1

1 * 1 = 1

1 * 2 = 2

End of inner loop

2 * 1 = 2

2 * 2 = 4

End of inner loop

3 * 1 = 3

3 * 2 = 6

End of inner loop

End of outer loop

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