cpet190_lect9

February 14, 2005February 14, 2005 Lecture 9 - By Paul LinLecture 9 - By Paul Lin 11

CPET 190 CPET 190

Problem Solving with MATLABProblem Solving with MATLAB Lecture 9Lecture 9

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


Lecture 9: MATLAB Program Design Lecture 9: MATLAB Program Design & Flow Control II& Flow Control II9-1 Control Flow – 9-1 Control Flow –

• if, else, elseif, endif, else, elseif, end• switch, case, otherwiseswitch, case, otherwise• forfor• whilewhile• break, continuebreak, continue

9-2 Loop Control9-2 Loop Control• forfor• whilewhile• break, continuebreak, continue

9-3 Conditional Statements9-3 Conditional Statements• if, else, elseif, endif, else, elseif, end


9-1 Control Flow9-1 Control FlowMATLAB Control Flow (keywords)MATLAB Control Flow (keywords)

• if, else, elseif, endif, else, elseif, end• switch, case, otherwiseswitch, case, otherwise• forfor• whilewhile• break, continuebreak, continue

Specifying conditions and selections Specifying conditions and selections • If, else, elseif, end If, else, elseif, end • switch-case statementsswitch-case statements

Repeating a set of commands or functions Repeating a set of commands or functions • ForFor• whilewhile


9-2 Loop Control9-2 Loop ControlFOR LoopFOR Loop FOR Repeat statements a specific number of times.FOR Repeat statements a specific number of times. The general form of a FOR statement is: The general form of a FOR statement is:

FOR FOR variable = n:s:mvariable = n:s:mstatement, ..., statement statement, ..., statement

ENDEND where where variablevariable is the loop counter, is the loop counter, nn is the initial is the initial

value, value, ss is the loop counter increment or decrement is the loop counter increment or decrement size, size, mm is the final value is the final value

Example:Example: for n = 1:10for n = 1:10

statement 1statement 1 statement 2statement 2

.... statement nstatement n endend


9-2 Loop Control9-2 Loop ControlExample 9-1: Nested For LoopsExample 9-1: Nested For Loops

% multiplytable.m% multiplytable.mN = 9; N = 9; A = zeros(N);A = zeros(N);for row = 1:N,for row = 1:N, for col = 1:N,for col = 1:N, A(row, col) = A(row, col) =

row * col;row * col; endendendenddisp(A)disp(A)

1 2 3 4 5 6 7 8 92 4 6 8 10 12 14 16 183 6 9 12 15 18 21 24 274 8 12 16 20 24 28 32 365 10 15 20 25 30 35 40 456 12 18 24 30 36 42 48 547 14 21 28 35 42 49 56 638 16 24 32 40 48 56 64 729 18 27 36 45 54 63 72 81


9-2 Loop Control9-2 Loop Control

Example 9-2: While loopExample 9-2: While loop

%whileloop.m%whileloop.mn = 1;n = 1;while n < 6while n < 6 disp(n)disp(n) n = n + 1;n = n + 1;endend

Output:

1

2

3

4

WHILE Loop - WHILE Loop - WHILE Repeat statements an indefinite number WHILE Repeat statements an indefinite number of times.of times.

The general form of a WHILE statement is: The general form of a WHILE statement is: WHILE expressionWHILE expression statementsstatementsENDEND


9-2 Loop Control9-2 Loop ControlTerminate Loop or Exit Conditional StatementsTerminate Loop or Exit Conditional Statements

• BreakBreak – stop execution of loop – stop execution of loop • Continue – Exit the inner loop and continuing on outer loopContinue – Exit the inner loop and continuing on outer loop

Example 9-3Example 9-3%break_continue.m%break_continue.mk = 1;k = 1;while k < 10while k < 10 x = 10 - k^2;x = 10 - k^2; if x < 0if x < 0 breakbreak endend y = sqrt(x)y = sqrt(x) k = k + 1;k = k + 1;endendfprintffprintf('The %d time in the loop -> x less than zero = %d\n', k, x);('The %d time in the loop -> x less than zero = %d\n', k, x);%The 4th time in the loop -> x %less than zero = -6%The 4th time in the loop -> x %less than zero = -6


9-2 Loop Control9-2 Loop ControlContinue StatementContinue Statement

• Continue – Pass control to the next iteration of Continue – Pass control to the next iteration of the FOR or WHILE loopthe FOR or WHILE loop

Example 9-4Example 9-4%continue_ex.m%continue_ex.mfor k=1:6for k=1:6 if k == 4;if k == 4; continuecontinue endend fprintf('k = %d\n', k); fprintf('k = %d\n', k); endenddisp('End of loop')disp('End of loop')

Output:Output:k = 1k = 1k = 2k = 2k = 3k = 3k = 5k = 5k = 6k = 6End of loopEnd of loop


9-3 Conditional Statements9-3 Conditional Statements Three Forms of if StatementsThree Forms of if Statements

• if-endif-end• if-else-endif-else-end• if-elseif-else-endif-elseif-else-end

IF- END format IF- END format • Single statementSingle statement

if conditionif condition statementstatementendend

• Multiple statementsMultiple statementsif conditionif condition

Statement_1;Statement_1; Statement_2;Statement_2; … ….. Statement_n;Statement_n;end end


9-3 Conditional Statements9-3 Conditional Statements

Example 9-5: compute only if x Example 9-5: compute only if x ≥ 0.≥ 0.

%inf_cond1.m%inf_cond1.mx = input('Enter a number: ')x = input('Enter a number: ')y_complex = y_complex = sqrt(x)sqrt(x)if x >= 0if x >= 0 y_real = y_real = sqrt(x)sqrt(x)endend% x = 2 % x = 2 % y_complex = 1.4142 % y_complex = 1.4142 % y_real = 1.4142% y_real = 1.4142% x = -2% x = -2% y_complex = 0 + 1.4142i% y_complex = 0 + 1.4142i

xy

Real Axis

Imaginary Axis

I or J operator90 degree

0 + 1.4142 j

1.4142


9-3 Conditional Statements9-3 Conditional Statements Example 9-6: A Grade Calculation Program – Example 9-6: A Grade Calculation Program –

Problem StatementProblem Statement

Compute average grade of three exams (input from Compute average grade of three exams (input from keyboard), then calculate and print a letter grade (on keyboard), then calculate and print a letter grade (on the screen) based on the following policy:the screen) based on the following policy:

A grade: Average >= 90A grade: Average >= 90B grade: 80 <= Avg < 90B grade: 80 <= Avg < 90C grade: 70 <= Avg <80C grade: 70 <= Avg <80D grade: 60 <= Avg < 70D grade: 60 <= Avg < 70F grade: Avg < 60F grade: Avg < 60


9-3 Conditional Statements9-3 Conditional Statements Example 9-6: A Grade Calculation Program – using Example 9-6: A Grade Calculation Program – using

FlowchartFlowchartStart

Avg >=90

80 <= Avg < 90

70 <= Avg < 8070 <= Avg < 80

60 <= Avg < 70

Avg < 60

End

Input T1, T2, and T3 Scores; Compute Average

Grade = ‘A’, Print

Grade = ‘B’, Print

Grade = ‘C’, Print

Grade = ‘D’, Print

Grade = ‘F’, Print

No

No

No

No

Yes

Yes

Yes

Yes

Yes


9-3 Conditional Statements9-3 Conditional Statements Example 9-6: A Grade Calculation Program – SolutionExample 9-6: A Grade Calculation Program – Solution

%grade_prog.m%grade_prog.mt1 = input('Enter Test 1 Score: ')t1 = input('Enter Test 1 Score: ')t2 = input('Enter Test 2 Score: ')t2 = input('Enter Test 2 Score: ')t3 = input('Enter Test 3 Score: ')t3 = input('Enter Test 3 Score: ')% Grade calculation% Grade calculation

avg = (t1 + t2 + t3)/3;avg = (t1 + t2 + t3)/3;if avg >= 90 if avg >= 90 Grade = 'A';Grade = 'A';endendif (avg >= 80) & (avg < 90) if (avg >= 80) & (avg < 90) Grade = 'B';Grade = 'B';endend

if (avg >= 70) & (avg < 80) if (avg >= 70) & (avg < 80) Grade = 'C';Grade = 'C';endendif (avg >= 60) & (avg < 70) if (avg >= 60) & (avg < 70) Grade = 'D';Grade = 'D';endendif avg < 60if avg < 60 Grade = 'F';Grade = 'F';endendfprintf('Your average score fprintf('Your average score is %g.\n', avg);is %g.\n', avg);fprintf('Your grade grade is fprintf('Your grade grade is %c.\n', Grade);%c.\n', Grade);



IF-ELSEIF-ELSE-END IF-ELSEIF-ELSE-END ifif expression expression statementsstatementselseif elseif expressionexpression statementsstatementselseelse statementsstatementsendend

ifif expression expression statements_1statements_1 elseifelseif statements_2statements_2 elseifelseif statements_3statements_3 elseelse statements_4statements_4 endend

IF-ELSE-ENDIF-ELSE-END Construct: Construct: if if expression expression statements_1statements_1elseelse statements_2statements_2endend



Example 9-7: A Full Wave RectifierExample 9-7: A Full Wave Rectifier

AC 60HzSine wave

RL = 100 ohms

VL

51 2 3

4

6

7

8910

10V110V

Transformer

Bridge Rectifier



Example 9-7: A Full Wave Rectifier Example 9-7: A Full Wave Rectifier Simulation using IF-END and FOR loop.Simulation using IF-END and FOR loop.

Pusedocode Pusedocode Transformer voltage ratio 110/10 voltsTransformer voltage ratio 110/10 volts e1 = 10*sin(2*pi*f*t); f = 60Hze1 = 10*sin(2*pi*f*t); f = 60Hz Rectifying signal e1Rectifying signal e1

If e1 < 0If e1 < 0 e1 = -e1;e1 = -e1;endend

Output – Full-wave rectified voltage (plot)Output – Full-wave rectified voltage (plot)


9-3 Conditional Statements9-3 Conditional StatementsExample 9-7: SolutionExample 9-7: Solution

%full_rec.m%full_rec.m% Primary side voltage% Primary side voltageVp = 110; Vp = 110; % secondary side voltage% secondary side voltageVs = 10; Vs = 10; % Frequency is 60 Hz% Frequency is 60 Hzf = 60; f = 60; % Period is 16.67 ms% Period is 16.67 msT = 1/f; dt = 10E-3*T;T = 1/f; dt = 10E-3*T;% For showing 2 cycles% For showing 2 cyclest = 0:dt:T; e1 t = 0:dt:T; e1

=Vs*sin(2*pi*f*t);=Vs*sin(2*pi*f*t);len = length(e1);len = length(e1);

% Rectifier operation% Rectifier operationfor n = 1: len,for n = 1: len, if e1(n) >= 0if e1(n) >= 0 e2(n) = e1(n);e2(n) = e1(n); elseelse e2(n) = -e1(n);e2(n) = -e1(n); endendendend

% continue on next % continue on next % slide% slide


9-3 Conditional Statements9-3 Conditional StatementsExample 9-7: Solution (cont.)Example 9-7: Solution (cont.)%full_rec.m%full_rec.mfigure(1), plot(t, e2, 'r', t, e1,'b--'), figure(1), plot(t, e2, 'r', t, e1,'b--'),

grid ongrid ontitle('Full Wave Rectifier')title('Full Wave Rectifier')xlabel('Time in sec')xlabel('Time in sec')ylabel('Volts')ylabel('Volts')

figure(2), subplot(2,1,1), plot(t, e1), figure(2), subplot(2,1,1), plot(t, e1), grid ongrid on

title('Input signal')title('Input signal')xlabel('Time in sec')xlabel('Time in sec')ylabel('Volts')ylabel('Volts')figure(2), subplot(2,1,2), plot(t, e2), figure(2), subplot(2,1,2), plot(t, e2),

grid ongrid ontitle('Full Wave Rectified Signal')title('Full Wave Rectified Signal')xlabel('Time in sec')xlabel('Time in sec')ylabel('Volts')ylabel('Volts')

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018-10

-5

0

5

10Input signal

Time in sec

Volts

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.0180

2

4

6

8

10Full Wave Rectified Signal

Time in sec

Volts


SummarySummary Control FlowControl Flow Loop ControlLoop Control

• forfor• whilewhile• break, continuebreak, continue

Conditional StatementsConditional Statements• if, else, elseif, endif, else, elseif, end

Next - Multiple Decision using switch, Next - Multiple Decision using switch, case, whatever, endcase, whatever, end

And More applicationsAnd More applications


Question?Question?

AnswersAnswers

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