MATLAB PROGRAMMING FOR ENGINEERS CH 3 BRANCHING STATEMENTS

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Matlab Programming for Engineers Introduction to Matlab Basics Branching Statements Loops User Defined Functions Additional Data Types Input/Output Functions Simulink Toolbox Important Toolboxes (if time is available) Dr. Nidal Farhat Mechanical Engineering Department 1

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS OBJECTIVES § The Logical Data Type § Relational Operators (==, ~=, >, < , >=, <=) § Logic Operators (&, &&, |, ||, xor, ~) § Logical Functions (ischar, isempty, …. ) § Branches § (if-else) Statement § switch Statement § try-catch Statement § Additional Plotting Features Mechanical Engineering Department 2

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS THE LOGICAL DATA TYPE (true, false) Mechanical Engineering Department 3

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS RELATIONAL OPERATORS (==, ~=, >, < , >=, <=) Some relational operations and their results Mechanical Engineering Department 4

CH 3: BRANCHING STATEMENTS MATLAB PROGRAMMING FOR ENGINEERS RELATIONAL OPERATORS (==, ~=, >, < , >=, <=) Compare array by a value Compare array by another one (of the same size) Mechanical Engineering Department Be careful because of roundoff errors 5

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS LOGIC OPERATORS Operator Operation & Logical AND (scalar/array, both sides evaluation) && Logical AND (scalar, left then right side evaluation) | Logical inclusive OR (scalar/array both sides evaluation) || Logical inclusive OR (scalar, left then right side evaluation) xor Logical exclusive OR ~ Logical NOT Mechanical Engineering Department 6

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS LOGIC OPERATORS EXAMPLE Mechanical Engineering Department 7

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS LOGICAL FUNCTIONS Mechanical Engineering Department 8

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS QUIZ! Mechanical Engineering Department 9

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Branches: a) if Statement Mechanical Engineering Department 10

CH 3: BRANCHING STATEMENTS MATLAB PROGRAMMING FOR ENGINEERS BRANCHES (if-STATEMENT) Optional Mechanical Engineering Department 11

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (if-STATEMENT) Example: § Write a program that determine whether a quadratic equation: has real (identical/different) or complex roots. (Use input command for entering the coefficients (a, b, c) and disp commands to display the output). § Write a program that calculates the roots in each case. (Use input command for entering the coefficients of the equation and disp commands to display the output). § Test the program on the following equations: Mechanical Engineering Department 12

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (if-STATEMENT) Example: evaluating a Function of Two Variables Test it using the following (x, y) values: Mechanical Engineering Department 13

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (if-STATEMENT) Nested if-Statements It is preferable to use if-else-end statement whenever is possible Mechanical Engineering Department 14

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Branches: b) switch Statement Mechanical Engineering Department 15

CH 3: BRANCHING STATEMENTS MATLAB PROGRAMMING FOR ENGINEERS BRANCHES (switch-STATEMENT) The switch statement syntax is a means of conditionally executing code. In particular, switch executes one set of statements selected from an arbitrary number of alternatives. The switch_expr and case_expr may be a scalar or a string Optional Mechanical Engineering Department 16

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (switch-STATEMENT) Remarks: § The case expression could be more than one enclosed by {} § At most one code block can be executed. If the switch_exp matches more than case_exp the first one is executed. Mechanical Engineering Department 17

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (switch-STATEMENT) Example: Mechanical Engineering Department 18

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (switch-STATEMENT) Example: Example Mechanical Engineering Department 19

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (switch-STATEMENT) Example Mechanical Engineering Department 20

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Branches: b) try/catch Statement Mechanical Engineering Department 21

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (try/catch) § The try/catch statement is designed to trap errors. § In MATLAB when an error is encountered while running the program execution is aborted. § Use try/catch statement to run a part of the program susceptible to produce error when executed. MATLAB will try to execute this part. If an error is produced, then instead of aborting, it executes the part of the program found in the catch statement. § If no error is produced in the try block, the catch block will not be executed. § The programmer can handle errors in the program without causing the program to stop. Mechanical Engineering Department 22

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (try/catch) Mechanical Engineering Department 23

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS BRANCHES (try/catch) Example Mechanical Engineering Department 24

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS fprintf command fprintf(format, data) Mechanical Engineering Department 25

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Example f(x) = sin(x), from -2π to 2π Then restrict the axes to the region 0 ≤ x ≤ π, and 0 ≤ y ≤ 1 Mechanical Engineering Department 26

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Plotting Multiple Plots on the Same Axes OR Mechanical Engineering Department 27

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Creating Multiple Figures Mechanical Engineering Department 28

CH 3: BRANCHING STATEMENTS MATLAB PROGRAMMING FOR ENGINEERS Additional plotting features Subplot(m, n, p) ≡ creates mxn subplots in the current figure (array of subplots), m rows and n columns. p is the current subplot. p=1 p=4 Mechanical Engineering Department p=2 p=3 p=[5 6] 29

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Enhanced Control of Plotted Lines plot(x, y, 'Property. Name', value, …) Mechanical Engineering Department 30

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Enhanced Control of Plotted Lines Example, Mechanical Engineering Department 31

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Enhanced Control of Text Strings Mechanical Engineering Department 32

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Enhanced Control of Text Strings Additional plotting features Mechanical Engineering Department 33

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Enhanced Control of Text Strings Examples: Mechanical Engineering Department 34

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Polar Plots polar(theta, r) Example, Mechanical Engineering Department 35

MATLAB PROGRAMMING FOR ENGINEERS CH 3: BRANCHING STATEMENTS Additional plotting features Polar Plots polar(theta, r) Solution: Mechanical Engineering Department 36