1. Review for Exam2 Key Ideas 1

2. Key Ideas: Boolean Operators (2 > 3) || (3 < 29.3) A.True B.False C.Impossible to determine (22 > 3) && (3 > 29.3) A.True B.False C.Impossible to determine (22 > x) && (x > 29.3) A.True B.False C.Impossible to determine (x = 2) A.True B.False C.Impossible to determine 2 What is the result of the following statement?

3. Key Ideas: if statements Decision (Conditional) Structure – To execute some part of code under certain circumstances only – To skip some part of a code 3 if elseif … else end

4. Key Ideas: switch Statements Decision (Conditional) Structure – To compare a single variable with multiple cases (equality) – To execute some part of code under the first matching case – To skip rest of a code 4 switch variable case specification 1. case specification n otherwise end

5. Key Ideas: Loops Matlab has two loops, one for each method explained previously: while – A CONDITIONAL loop. Generic, all-purpose. Best used when the programmer does not know how many times the block of code needs to repeat. – Repeats while CONDITION is true. for – A COUNTING loop. Best used when the programmer “knows” how many times the block of code needs to repeat. 5

6. Key Ideas: while Loop A while loop repeats a block of code while a condition is true. Loop variable(s) Structure: Initialization, while condition, code to be repeated, update of condition, end Common Uses: – trap the user until a valid input is given (relational operators, even, odd, integers, etc.) – running total until a condition is met Infinite loop occurs when the loop condition is never updated to a false condition while in the loop – To stop an infinite loop: Ctrl-C 6

7. Key ideas: for Loop The for loop is a counting loop The while loop can always be used BUT…the for loop is meant to count – The startvalue:step:endValue contains all necessary values for the loop to work. Nested for loops are absolutely possible! Actually, any construct ( if, switch, while, for ) can now be nested within each other. 7

8. Review for Exam2 Questions 8

9. Review Questions Loops:  Match the following a.for1. does not exist in Matlab b.while2. number of iterations is known c.do/while3. unknown number of iterations 9

10. Review Questions  After prompting the user how many values should be entered, what loop is most appropriate to prompt for each grade separately?  Nested within the 1 st loop, which loop can be used to trap the user until s/he enters a valid value? 10 a.for b.while c.switch d.if a.for b.while c.switch d.if

11. Review Questions Loops: X = -1; while X <=0 Y = X + 1; end The code above will result in an infinite loop 11 a.True b.False

12. Review Questions Loops: X = -1; while X <=0 x = X + 1; end The code above will result in an infinite loop 12 a.True b.False

13. Review Questions Loops: X = -1; while X <=0 X = X + 1; end The code above will result in an infinite loop 13 a.True b.False

14. Review Questions X1 = 4; X2 = 7; while ____(x1-x2)>0.0002 % code.. end  In numerical methods, what function is commonly used to check if two values are “close enough”? 14

15. Review Questions Using the following code: for r = 1:3 for c = 1:4 x = input(‘An integer: ‘); end  How many times will the input() command execute?  In general, what is the result? 15

16. Review Questions Using the following code: for position = 1:2:14 disp(‘*’) end  How many stars will print to the screen? 16

17. Review Questions  Using the following code, fill in the blanks to answer. result = 0; for x = 3:5 for y = 1:2 for z = 10:10:20 result = result + x*y*z; end result = 0 + 3*1*10+ ______ + _____ + ______ + ______ + _____ + ____ + _____. 17

18. Review Questions  How many stars will print to the screen? _____ for position = 14:2:1 disp(‘*’) end 18

19. Review Questions Library functions:  What is the range of the following equations: a. floor(rand*12+3) b. ceil(rand*5+1) c. rand*10+5 19

20. Review Questions Modulus:  The following code Is true only if x is 20 a.odd b.even c.fraction

21. Example Problem Below are two formulas for calculating π: Write a MATLAB program that – 1) Calculate the value of pi using the first formula and let the term to add up until the error is within 0.000001. Keep track the number of terms. – 2) Calculate the value of pi using the second formula with the same number of terms. – 3) Output pi values from step 1 and 2 (8 decimal places), as well as the error in the step 2 as a percentage (4 decimal places). 21

22. Example Problem, cont’d Write a MATLAB program that – 1) Calculate the value of pi using the first formula and let the term to add up until the error is within 0.000001. Keep track the number of terms. – 2) Calculate the value of pi using the second formula with the same number of terms. – 3) Output pi values from step 1 and 2 (8 decimal places), as well as the error in the step 2 as a percentage (4 decimal places). 22

23. STUDY HARD! Practice tonight. Take the notes you just took, and code the example! The more practice, the easier it gets! 23