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Introduction to Engineering MATLAB - 13

Introduction to Engineering MATLAB - 13. Agenda Conditional statements If – end If – else – end if – elseif – else - end. CONDITIONAL STATEMENTS. Conditional statements enable MATLAB to make decisions. The process is similar to the way we (humans) make decisions.

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Introduction to Engineering MATLAB - 13

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  1. Introduction to EngineeringMATLAB - 13 Agenda Conditional statements If – end If – else – end if – elseif – else - end

  2. CONDITIONAL STATEMENTS • Conditional statements enable MATLAB to make decisions. • The process is similar to the way we (humans) make decisions. • A condition stated. If the condition is met, one set of actions is taken. If the condition is not met, either nothing is done, or a second set of actions is taken. Example: If I win the Lottery, I will quit college, buy a new car, and go fishing. If I do not win the Lottery, I will study harder so that I can get a better job.

  3. Conditional Statements • NEED AN EXAMPLE OF HOW “IF…ELSE” STATEMENTS RUN IN A PRORGAM; E.G. MACHINERY IN A FACTORY

  4. THE FORM OF A CONDITIONAL STATEMENT if variableRelational operatorvariable or a number Relational operatorMeaning < Less than. <= Less than or equal to. > Greater than. >= Greater then or equal to. == Equal to. ~= Not equal to.

  5. EXAMPLES OF CONDITIONAL STATEMENTS Variable previously defined or a number variable If a < b If c >= 5 If a == b If a ~= 0 Relational operator

  6. Logical OperatorNameMeaning & AND True if both conditional statements are true. | OR True if either or both conditional statements are true. ~ NOT True if the conditional statement is false ADDING LOGICAL OPERATORS TO CONDITIONAL STATEMENTS

  7. EXAMPLES OF LOGICAL OPERATORS IN CONDITIONAL STATEMENTS if (d < h) & (x >= 7) True if d is smaller than h and x is equal or larger than 7. if (x ~= 13) | (y < 0) True if x is not equal to 13 and/or if y is smaller than 0. If ~(x == y) True if x is not equal to y.

  8. THE THREE FORMS OF THE if STATEMENT Ifconditional statement commands end ifconditional statement 1 command group 1 elseifconditional statement 2 command group 2 else command group 3 end ifconditional statement command group 1 else command group 2 end

  9. if weight ≥ 11.75 oz. False If weight ≥ 11.75 oz. Put can in package end True Put can in package end Example: if-end STATEMENT • In a soft drink factory, every can is weighed, and if it weighs 11.750 oz. or more, it is put in a package

  10. if False CONDITIONAL STATEMENT True COMMANDS end THE if – end STATEMENT Flowchart of the if – end statement: Ifconditional statement commands end

  11. EXAMPLE OF USING THE if – end STATEMENT % A script file that demonstrates the use of the if-end statement. % The user is asked to enter three grades. % The program calculates the average of the grades. % If the average is less than 60, a massage: % The student did not pass the course. is printed. score = input('Enter (as a vector) the scores of the three tests '); ave_grade = (score(1) + score(2) + score(3))/3; disp('The average grade is:') disp(ave_grade) if ave_grade < 60 disp('The student did not pass the course.') end

  12. EXAMPLE OF USING THE if – end STATEMENT Executing the script file of the previous slide in the Command Window: >> Lecture8Example1 Enter (as a vector) the scores of the three tests [78 61 85] The average grade is: 74.6667 >> Lecture8Example1 Enter (as a vector) the scores of the three tests [60 38 55] The average grade is: 51 The student did not pass the course.

  13. THE if – else - end STATEMENT Flowchart of the if – else – end statement: if False ifconditional statement command group 1 else command group 2 end CONDITIONAL STATEMENT True COMMAND GROUP 1 COMMAND GROUP 2 end

  14. EXAMPLE OF USING THE if – else - end STATEMENT % A script file that demonstrates the use of the if-else-end statement. % The user is asked to enter three grades. The program calculates % the average of the grades. If the average is less than 60, a % massage: The student did not pass the course. is printed. % Otherwise, a massage: The student passed the course. is printed. score = input('Enter (as a vector) the scores of the three tests '); ave_grade = (score(1) + score(2) + score(3))/3; disp('The average grade is:') disp(ave_grade) if ave_grade < 60 disp('The student did not pass the course.') else disp('The student passed the course.') end

  15. EXAMPLE OF USING THE if - else – end STATEMENT Executing the script file of the previous slide in the Command Window: >> Lecture8Example2 Enter (as a vector) the scores of the three tests [65 80 83] The average grade is: 76 The student passed the course. >> Lecture8Example2 Enter (as a vector) the scores of the three tests [60 40 55] The average grade is: 51.6667 The student did not pass the course.

  16. THE if – elseif – else – end STATEMENT ifconditional statement 1 command group 1 elseifconditional statement 2 command group 2 else command group 3 end

  17. FLOWCHART OF THE if – elseif – else – end STATEMENT if False CONDITIONAL STATEMENT 1 elseif False CONDITIONAL STATEMENT 2 True COMMAND GROUP 1 True COMMAND GROUP 3 COMMAND GROUP 2 end

  18. In-Class Exercise • Create a real-life situation that uses “if-else or if-else-if statements • Create a flow-chart showing the following: • The logic for the sorter and your team’s conveyor system • The logic for your team’s counter

  19. EXAMPLE OF USING THE if – elseif – else – end STATEMENT % A script file that demonstrates the use of the if-elseif-else-end % statement. % The program calculates the tip in a restaurant according to the % amount of the bill. % If the bill is less than $10 the tip is $1.80. % Between $10 and $60 the tip is 18% of the bill. % Above $60 the tip is 20% of the bill. format bank clear tip (The file continues on the next slide)

  20. (Continuation from the previous slide) bill = input('Enter the amount of the bill (in dollars): '); if bill <=0 disp('Error. The amount can not be zero or negative') elseif (bill > 0) & (bill <= 10) tip = 1.8; disp('The tip is (in dollars):') disp(tip) elseif (bill > 10) & (bill <= 60) tip = bill*0.18; disp('The tip is (in dollars):') disp(tip) else tip = bill*0.2; disp('The tip is (in dollars):') disp(tip) end

  21. EXECUTING THE SCRIPT FILE OF THE RESTAURAT TIP CALCULATION >> Lecture8Example3 Enter the amount of the bill (in dollars): 15 The tip is (in dollars): 2.70 >> Lecture8Example3 Enter the amount of the bill (in dollars): -21 Error. The amount can not be zero or negative >> Lecture8Example3 Enter the amount of the bill (in dollars): 6 The tip is (in dollars): 1.80 >> Lecture8Example3 Enter the amount of the bill (in dollars): 100 The tip is (in dollars): 20.00

  22. COMMENTS ABOUT if STATEMENTS • For every if command a computer program must have an end command. • A program can have many if ….. end statements following each other. • A computer program can perform the same task using different combinations of if - end, if – else – end, and if – elseif – else – end statements.

  23. Assignment #9 Problem 25 page 61 in the textbook. • Submit a printout of the script file and a printout of the command window when the script file was used for the different values of x. Problem 14 page 217 in the textbook. • Submit a printout of the function file and a printout of the command window when the function was used for the different values of W.

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