Matlab Programming for Engineers Introduction to Matlab 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

Relational Operators (==, ~=, >, < , >=, <=) 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

THE LOGICAL DATA TYPE (true, false)

RELATIONAL OPERATORS (==, ~=, >, < , >=, <=) Some relational operations and their results

RELATIONAL OPERATORS (==, ~=, >, < , >=, <=) Be careful because of roundoff errors Compare array by a value Compare array by another one (of the same size)

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

LOGIC OPERATORS EXAMPLE

LOGICAL FUNCTIONS

QUIZ!

Branches: a) if Statement

BRANCHES (if-STATEMENT) Optional

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:

BRANCHES (if-STATEMENT) Example: evaluating a Function of Two Variables Test it using the following (x,y) values:

BRANCHES (if-STATEMENT) Nested if-Statements It is preferable to use if-else-end statement whenever is possible

Branches: b) switch Statement

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

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.

BRANCHES (switch-STATEMENT) Example:

BRANCHES (switch-STATEMENT) Example: Example

BRANCHES (switch-STATEMENT) Example

b) try/catch Statement Branches: b) try/catch Statement

BRANCHES (try/catch) The try/catch statement is designed to trap errors. In MATLAB when an error is encountered while running the program 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.

BRANCHES (try/catch)

BRANCHES (try/catch) Example

fprintf command fprintf(format,data)

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

Additional plotting features Plotting Multiple Plots on the Same Axes OR

Additional plotting features Creating Multiple Figures

Additional plotting features Subplots 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=2 p=3 p=4 p=[5 6]

Additional plotting features Enhanced Control of Plotted Lines plot(x,y,'PropertyName',value,…)

Additional plotting features Enhanced Control of Plotted Lines Example,

Additional plotting features Enhanced Control of Text Strings

Additional plotting features Enhanced Control of Text Strings

Additional plotting features Enhanced Control of Text Strings Examples:

Additional plotting features Polar Plots polar(theta,r) Example,

Additional plotting features Polar Plots polar(theta,r) Solution: