1. Selection Programming EE 100

2. Outline introduction Relational and Logical Operators Flow Control Loops Update Processes

3. Introduction Programs commands in MATLAB are executed in sequence. The sequence can be altered using programming structures (control flow -if, switch-, repetition- for, while-). Decision can be made using relational and logical expressions. (a check if a condition is met or not)

4. Relational and Logical Operators For more information: help ops.

5. Relational and Logical Operators For relational and logical expressions: Inputs: True is any nonzero number False is 0 (zero) Outputs: True is 1 (one) False is 0 (zero) An output array variable assigned to a relational or logical expression is identified as logical.

6. Relational and Logical Functions

7. Flow Control Simple if Statement The general form of a simple if statement is: if logical expression commands end Example: if d < 50 count = count + 1; disp(d); end

8. Flow Control Nested if Statements : general form if logical expression commands if logical expression Commands end

9. Flow Control Example: Nested if Statements if d < 50 count = count + 1; if count > 10 disp(‘count > 10’); end

10. Flow Control- else and elseif Clauses General form if logical expression commands else commands end General form if logical expression commands elseif logical expression commands elseif logical expression Commands else Commands end

11. Flow Control- else and elseif Clauses Example: If average > 86 disp(‘Excellent’) elseif average > 76 disp(‘Very good’) elseif average > 68 disp(‘Good’) else disp(‘Ya 7aram- accepted’) end

12. Flow Control- Switch Structure General form: switch expression case test expression 1 commands case {test expression 2, test expression 3} commands ··· otherwise commands end

13. Flow Control- Switch Structure Example: d = floor(3*rand) + 1 switch d case 1 disp( ’That’’s a 1!’ ); case 2 disp( ’That’’s a 2!’ ); otherwise disp( ’Must be 3!’ ); end Example: d = floor(10*rand); switch d case {2, 4, 6, 8} disp( ’Even’ ); case {1, 3, 5, 7, 9} disp( ’Odd’ ); otherwise disp( ’Zero’ ); end

14. Loops- for loop General form: for index = j:k statements end or for index = j:m:k statements End Floor (last − first)/increment + 1 for i = 1:5 disp(i) end for i = 1:2:5 disp(i) end

15. Loops- while loop General form while condition statements end Example: count = 0; While count < 5 disp (count) count= count + 1; end

16. Loops- while loop - break Example: count = 0; While count < 5 disp (count) count= count + 1; If count == 4 Break end

17. Avoiding loops In general, loops should be avoided in Matlab, as they can significantly increase the execution time of a program. The execution time increases as MATLAB allocate memory each time through the loop. Usually avoid loops by vectorizing.

18. Avoiding loops example: vectorizing tic n = 1:10000000; s = sum( n ); toc elapsed_time = 0.5300 example: loop tic s = 0; for n = 1:10000000 s = s + n; end toc elapsed_time = 23.6840

19. Update Processes Many problems in science and engineering involve modeling a process where the main variable is updated over a period of time. In many situations, the updated value is a function of the current value.

20. Thank You