Thinking Like an Engineer. Instructor Slides

Transcription

1 Instructor Slides Thinking Like an Engineer An Active Learning Approach Stephan, Bowman, Park, Sill, Ohland Third Edition Copyright 2015 Pearson Prentice-Hall, Inc.

2 Create relational expressions using relational operators. Combine relational expressions using logical operators to form logical expressions. Create and use logical variables in decisions. Design logic within the constraints of the priority of operators. Apply selected functions to logical variables (STRCMPI). Predict the number of possible outcomes and the actual result of a conditional statement. Determine if two conditional statements are logically equivalent. Utilize single or nested conditional statement structures with a program (IF/ELSEIF/ELSE).

3 Motivation: Give computers decision making authority. Computers: Can make binary decisions based on binary arguments The only decision a computer can make: TRUE FALSE (or YES- NO or 1-0) MATLAB: Can ask yes/no questions and conditionally execute code based on the outcome of the questions.

4 IF Q1 T IF Q1 Yes F No IF Q1 1 0

5 Single IF Statement 3 parts: Question, True, False = IF (Q, T, F) IF Q T F

6 if o Ask question. The Condition portion can contain o simple Write block relational of code what to do if true expressions or complex expressions built with with instruction on TRUE option combinations of logic and relational operators. else what to do if false o o o Designate the of the operations completed if the logical statement is true. Write block of code with instruction on FALSE option. Designate the of the IF statement.

7 You must test each branch of your algorithm! For each diamond, need TWO test cases. Branch T F IF Q F Test Case If Q is true If Q is false T

8 Greater than Less than Greater than or equal to Equal to Less than or equal to Not equal to

9 if Insert Condition Insert MATLAB Code (True) if Insert Condition Insert MATLAB Code (True) else Insert MATLAB Code (False) X = 5; if X < 10 X = X + 3; M = 20; if M >= 20 else M = 0; M = 1;

10 Ask the user to enter their age in years. If the user enters a negative number, warn the user and use the absolute value. Age = input('enter your age'); if Age < 0 warning('you entered a negative value. Using absolute value.') Age = abs(age);

11 Ask the user to enter circumference of a sphere in units of centimeters. Determine the volume of a sphere in units of liters. If the user enters a negative value for circumference, use an error message to terminate the program. C = input('enter the circumference [cm]'); if C < 0 error('you entered a negative value.') else d = C / pi; r = d / 2; V = 4/3 * pi * r^3

12 We want to take the square root of the sum of two variables, A and B. If the sum of A and B is negative, display a warning message, and calculate the square root of the absolute value; otherwise, calculate the square root of the sum of A and B. A = 5; B = 10; if A + B < 0 warning('error: A+B is negative, use absolute value\n') else Y = sqrt(abs(a+b)); Y = sqrt(a+b);

13 MATLAB converts decimal values to binary numbers. Some decimals up with errors in the 16 th decimal place. In the Command Window, type: x = 1.6 fprintf('%0.16f',x) Result: Note the residual "1" in the 16 th decimal place.

14 In the Command Window, type: x = 1.5; y = 3; if y == (3.2*x)/1.6 fprintf('yes\n') else fprintf('no\n') fprintf('%0.16f\t\t%0.16f',3.2*x/1.6,y) Moral of the Story Be very careful using == as a test for IF. Result: NO

15 IF Q1 T1 F1 IF Q2 T2 F2

16 Single IF Statement 3 parts: Question, True, False Nested IF Statements F1 =IF(Q1,T1,IF(Q2,T2,F2)) = IF (Q, T, F) T IF Q F IF Q1 F1 IF Q2 T1 T2 F2

17 if o Ask Question 1. what to do if Q1 true o Write block of code with instruction on TRUE option. elseif what to do if Q2 true o Ask Question 2. o Write block of code with instruction on TRUE option. else what to do if false o o o Designate the of the operations completed if the logical statement is true. Write block of code with instruction on FALSE option. Designate the of the if statement.

18 You must test each branch of your algorithm! For each diamond, need TWO test cases. Branch T1 F1 T2 F2 Test Case If Q1 is true If Q1 is false If Q2 is true If Q2 is false IF Q1 IF Q2 F1 F2 T1 T2

19 a = 4; b = 2; if a > 3 fprintf('%0.0f ',a) elseif a < 5 fprintf('%0.0f ',b) What values will display in the Command Window? A. 4 2 B. 2 C. 4 C D E. Nothing will display

20 Based on the user choice, save the food name in the text variable food. Assume user does not close window without making a choice. Use if elseif else commands. If the user chooses option #1, their favorite food is pizza; otherwise if the user chooses #2, it is tacos; otherwise if the user chooses #3, it is ice cream; otherwise it is spinach. 4 outcomes = 3 decisions Use if, elseif, elseif, else sequence

21 if food == 1 favorite = 'pizza' elseif food == 2 favorite = 'tacos' elseif food == 3 favorite = 'ice cream' else favorite = 'spinach'

22 Based on the user choice, save the food name in the text variable food. Use if elseif else commands. What happens if user closes window without making a choice?

23 if food == 1 favorite = 'pizza' elseif food == 2 favorite = 'tacos' elseif food == 3 favorite = 'ice cream' elseif food == 4 favorite = 'spinach' else fprintf('you did not make a selection')

24 At one atmosphere of pressure, water changes phases based upon temperature. Temperature [ C] Phase < 0 Solid Liquid > 100 Gas Create an program to determine the phase of water stored as text given the input temperature by the user in degrees Fahrenheit [ F].

25 If the water is at or less than zero Celsius [ C], it is solid; otherwise if the water is 100 degrees Celsius [ C] or greater, it is vapor; otherwise it is a liquid. 3 outcomes = 2 decisions Use if, elseif, else sequence Use the English as a guide. The commas separate the conditions from the actions. The semicolons separate the questions. The period marks the of the statement.

26 if T <= SLlim phase = 'solid' elseif T >= LGlim phase = 'vapor' else phase = 'liquid'

27 At one atmosphere of pressure, water changes phases based upon temperature. Temperature [ C] Phase < 0 Solid Liquid > 100 Gas Create a program to determine the phase of water stored as text given the input temperature by the user in degrees Fahrenheit [ F]. As output, tell the user the temperature entered and the phase. If the user enters a value below the physical possible limit of the temperature scale, inform the user of the mistake and terminate the program.

28 if T <= Tlim error('temperature is not physically possible.') if T <= SLlim phase = 'solid' elseif T >= LGlim phase = 'vapor' else phase = 'liquid'

29 if what to do if Q1 true else if what to do if Q2 true else o Ask Question 1. o o Write block of code with instruction on TRUE option. Designate the of the operations completed if the first logical statement is true. o Ask Question 2. o o Write block of code with instruction on TRUE option. Designate the of the operations completed if the second logical statement is true. what to do if false o Write block of code with instruction on FALSE option. o o Designate the of the second IF statement. Designate the of the second IF statement.

30 IF / ELSEIF IF / ELSE IF a = 4; b = 2; if a > 3 fprintf('%0.0f ',a) elseif a < 5 fprintf('%0.0f ',b) a = 4; b = 2; if a > 3 fprintf('%0.0f ',a) else if a < 5 fprintf('%0.0f ',b)

31 If the Reynolds number of a fluid flowing in a pipe is less than 2,000, the flow is laminar; otherwise, if the Reynolds number is greater than 10,000, the flow is turbulent; otherwise, it is considered transitional flow. Method 1 elseif Method 2 else if if Re < 2000 flow='laminar'; if Re < 2000 flow='laminar'; elseif Re > flow='turbulent'; else flow='transition'; else if Re > flow='turbulent'; else flow='transition';

32 AND Ampersand (&) True if ALL TRUE OR Pipe ( ) False if ALL FALSE NOT Tilde (~) Inverts logic

33

34 z = 3; if (z > 1) (z < 3) fprintf('%0.0f ',z) What will be displayed in the Command Window? A. 1 3 B D C. 1 D. 3 E. Nothing will display.

35 if (m >= 2) && (m < 6) fprintf('%0.0f ',m) What integer values of m will display in the Command Window? A. 2 6 B C C D. Any value will work. E. Nothing will display.

36 if (m >= 2) (m < 6) fprintf('%0.0f ',m) What integer values of m will display in the Command Window? A. 2 6 B D C D. Any value will work. E. Nothing will display.

37 x = 3; y = 5; if (x > 1) && (x < 3) fprintf('%0.0f ',x) else fprintf('%0.0f ',y) What values will display in the Command Window? A. 5 A B. 3 C. 3 5 D. 1 2 E. Nothing will display.

38 if (p > 0) && (p ~= 3) && (p <= 5) fprintf('%0.0f ',p) What integer values of p will display in the Command Window? A B B C D. Any value will work. E. Nothing will display.

39 if (p > 0) (p ~= 3) && (p <= 5) fprintf('%0.0f ',p) What integer values of p will display in the Command Window? A B D C D. Any value will work. E. Nothing will display.

40 Ask the user to enter the number of times they have seen their favorite movie, using an integer between 0 and 5. Store the result in a variable named MovieNumA. If the user enters a value less than zero or greater than 5, issue an error message to the user telling them if their value was too high (greater than 5) or too low (less than zero) and terminate the program.

41 Ask the user to enter temperature and pressure readings from a reactor. If the temperature is greater than zero but less than 100 degrees Celsius [ C] and the pressure is greater than 1 and less than 2 atmospheres [atm], print "Status: Normal Operation" in the Command Window. If the temperature or pressure readings are outside the normal range, print "Status: WARNING! Adjust operating parameters!" in the Command Window.

42 High blood pressure is classified as a pressure reading greater than 140 millimeter of mercury [mm Hg] systolic or 90 millimeter of mercury [mm Hg] diastolic in a middle-aged adult. For young adults, this range is classified as follows: Age Systolic Pressure [mm Hg] Diastolic Pressure [mm Hg] You are developing a blood pressure sensor that will take into account the user's age when making a diagnosis. Assume the user will input their age and pressure readings in millimeters of mercury. Indicate as output if the user has high blood pressure or has normal blood pressure. If the age range entered is not between 15 and 24 years old, indicate the user should not use this method of diagnosis.