Lecture 3 Programming in MATLAB. Dr. Bedir Yousif

Transcription

1 Lecture 3 Programming in MATLAB Dr. Bedir Yousif

2 RELATIONAL AND LOGICAL OPERATORS Relational operator Description < Less than > Greater than <= Less than or equal to >= Greater than or equal to = = Equal to ~= Not Equal to

3 RELATIONAL AND LOGICAL OPERATORS Some examples are:

4 RELATIONAL AND LOGICAL OPERATORS Some examples are:

5 RELATIONAL AND LOGICAL OPERATORS Some examples are: B =

6 RELATIONAL AND LOGICAL OPERATORS Some examples are:

7 RELATIONAL AND LOGICAL OPERATORS Some examples are:

8 Logical operators Logical operators in MATLAB are:

9 some examples Logical operators

10 some examples Logical operators

11 Priority of calculation expression Arithmetic, relational, and logical operators can be combined in mathematical expressions. Precedence Operation 1 (highest) Parentheses (if nested parentheses exist, inner ones have precedence) 2 Exponentiation 3 Logical NOT (~) 4 Multiplication, division 5 Addition, subtraction 6 Relational operators (>, <, >=, <=, = =, ~=) 7 Logical AND (&) 8 (lowest) Logical OR ( )

12 Examples of expressions that include arithmetic, relational, and logical operators:

13 Examples of expressions that include arithmetic, relational, and logical operators:

14 Built-in logical functions These functions are: and(a,b) equivalent to A&B or(a,b) equivalent to A B not(a) equivalent to ~A

15 Built-in logical functions

16 Built-in logical functions

17 Example: Analysis of temperature data The following were the daily maximum temperatures (in F) in Washington, DC, during the month of April 2002: (data from the U.S. National Oceanic and Atmospheric Administration). Use relational and logical operations to determine the following: (a) The number of days the temperature was above 75. (b) The number of days the temperature was between 65 and 80. (c) The days of the month when the temperature was between 50 and 60.

18 Example: Analysis of temperature data Solution >> t=[ ]; n=sum(t>=75) n = 7 >> n1=sum(t>=65 & t<=80) n1 = 12 >> n2=find(t>=50 & t<=60) n2 =

19 3.2 CONDITIONAL STATEMENTS if conditional expression consisting of relational and/or logical operators. Examples: Note that All the variables must have assigned values. a=20; b=-1;c=10; if a<b c=500;end >> a=20; b=-1;c=10; if a>b c=500;end

20 3.2 CONDITIONAL STATEMENTS The if-end Structure

21 3.2 CONDITIONAL STATEMENTS Example 3-2: Calculating worker s pay A worker is paid according to his hourly wage up to 40 hours, and 50% more for overtime. Write a program in a script file that calculates the pay to a worker. The program asks the user to enter the number of hours and the hourly wage. The program then displays the pay.

22 3.2 CONDITIONAL STATEMENTS Solution t=input('please enter the number of hours worked '); h=input('please enter the hourly wage in $ '); Pay=t*h; if t > 40 Pay=Pay+(t-40)*0.5*h; end fprintf('the workers pay is $ %5.2f',Pay)

23 3.2 CONDITIONAL STATEMENTS Program output Please enter the number of hours worked 35 Please enter the hourly wage in $ 8 The worker s pay is $ >> Workerpay Please enter the number of hours worked 50 Please enter the hourly wage in $ 10 The worker s pay is $

24 The if-else-end Structure

25 The if-elseif-else-end Structure

26 Example 3.3 A 3-bit A/D converter, with an analog input x and digital output y, is represented by the equation: y = 0 x < -2.5 = x < -1.5 = x < -0.5 = x < 0.5 = x < 1.5 = x < 2.5 = x < 3.5 = 7 x 3.5

27 Solution function Y_dig = bitatd_3(x_analog) % bitatd_3 is a function program for obtaining % the digital value given an input analog signal % usage: Y_dig = bitatd_3(x_analog) % Y_dig is the digital number (in integer form) % X_analog is the analog input (in decimal form) if X_analog < -2.5 Y_dig = 0; elseif X_analog >= -2.5 & X_analog < -1.5 Y_dig = 1; elseif X_analog >= -1.5 & X_analog < -0.5 Y_dig = 2; elseif X_analog >= -0.5 & X_analog < 0.5 Y_dig = 3; elseif X_analog >= 0.5 & X_analog < 1.5 Y_dig = 4; elseif X_analog >= 1.5 & X_analog < 2.5 Y_dig = 5; elseif X_analog >= 2.5 & X_analog < 3.5 Y_dig = 6; else Y_dig = 7; end Y_dig; end

28 when the latter program is executed,are y1 = bitatd_3(-1.25) y2 = bitatd_3(2.57) y3 = bitatd_3(6.0) y1 = 2 y2 = 6 y3 = 7

29 3.3 THE switch-case STATEMENT

30 3.3 THE switch-case STATEMENT Switch compares the input expression to each case value. Once the match is found it executes the associated commands. x = ceil(10*rand); % Generate a random integer in {1, 2,..., 10} switch x case {1,2} disp('probability = 20%'); case {3,4,5} disp('probability = 30%'); otherwise disp('probability = 50%'); End

31 After executes the associated commands. for k = 1:10 fswitch end Probability = 50% Probability = 30% Probability = 50% Probability = 50% Probability = 50% Probability = 30% Probability = 20% Probability = 50% Probability = 30% Probability = 50%

32 for index = expression statement group X End Example sum = 0; for i = 1:100 sum = sum + i^2; end Sum sum = FOR LOOPS

33 3.5 WHILE LOOP The general form of the WHILE loop is while expression 1 statement group 1 end statement group 2 When expression 1 is true, statement group 1 is executed. if expression 1 is false, the program exits the while loop and executes statement group 2.

34 3.5 WHILE LOOP Example 3.5:Determine the number of consecutive integer numbers which when added together will give a value equal to or just less than 210. int = 1; int_sum = 0; max_val = 210; while int_sum < max_val int_sum = int_sum + int; int = int + 1; end last_int = int if int_sum == max_val num_int = int - 1 tt_int_ct = int_sum elseif int_sum > max_val num_int = int - 1 tt_int_ct = int_sum - last_int end end

35 3.5 WHILE LOOP The solution obtained will be last_int = 21 num_int = 20 tt_int_ct = 210 Thus, the number of integers starting from 1 that would add up to 210 is 20. That is, =210

36 Thanks