MAT - Conditional Statements

1. MAT - Conditional Statements Programming in MATLAB / Chapter 6 Topics Covered: 1. if based conditional statements. if–end if-else–end if-elseif-else–end 2.switch-case P. 1

2. 174- 179 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. P. 2

3. 174 THE FORM OF A CONDITIONAL STATEMENT if Conditional expression consisting of relational and/or logical operators Examples: if a < b if c >= 5 if a == b if a ~= 0 if (d < h) & (x > 7) if (x ~= 13) | (y < 0) All variables must have assigned values. P. 3

4. 174- 179 FORMS OF THE if STATEMENT if conditional statement 1 command group 1 elseifconditional statement 2 command group 2 … (Optional) elseifconditional statement # command group # … (Optional) else %no conditional statement command group n+1 end if conditional statement command group end if conditional statement command group 1 else command group 2 end P. 4

5. 178- 179 THE if–elseif-else-end STATEMENT ...... ...... if conditional expression ........ ........ ........ elseif conditional expression ........ ........ ........ else ........ ........ ........ end ...... MATLAB program. Group 1 of MATLAB commands. Group 2 of MATLAB commands. Group 3 of MATLAB commands. MATLAB program. Examples of if-end and if-else-end can be found on pages 174-179 of the text P. 5

6. USING THE if–elseif-else-end STATEMENT Write program that calculates tip based on amount of bill, using the following rules • Bill less than $10 • Tip is $1.80 • Bill between $10 and $60 • Tip is %18 • Bill above $60 • Tip is %20 P. 6

7. 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 (The file continues on the next slide) P. 7

8. Note how tip’s value is control by ; and the disp command USING THE if–elseif-else-end STATEMENT bill = input('Enter the amount of the bill (in dollars): '); if (bill <= 10) tip = 1.8; elseif (bill > 10) & (bill <= 60) tip = bill*0.18; else tip = bill*0.2; end disp('The tip is (in dollars):') disp(tip) P. 8

9. USING THE if–elseif-else-end STATEMENT >> 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): 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 P. 9

10. 174- 179 COMMENTS ABOUT if–end STATEMENTS • For every if command 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. • Multiple elseif conditions are allowed within an if– elseif – else – end statement. • An else condition is not required. • When else is used, a conditional statement is NOT added P. 10

11. 180- 184 THE switch-case STATEMENT • switch-case is similar to if-elseif-end, except must be an exact match. You cannot use switch-case with a range, such as <0. • switch on scalar or string • otherwise == else (optional) P. 11

12. 180- 184 THE switch-case STATEMENT x = input (‘Resistance: ‘); switch x case 100 out= x; case 200 out= 2*x; case 300 out= 3*x; case 400 out= 4*x; otherwise out = 0; end P. 12

13. 180- 184 THE switch-case STATEMENT x = input (‘Purchase Class: ‘,’s’); x = upper(x) %change to upper case switch x case ‘A’ rate = 2.00; case ‘B’ rate = 3.00; case ‘C’ rate = 3.50; case ‘D’ rate = 4.00; otherwise rate = 0; end P. 13