ch4: loops mechanical engineering department matlab programming for engineers 1 matlab programming...

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Mechanical Engineering Department

MATLAB PROGRAMMING FOR ENGINEERS

Matlab Programming for Engineers Matlab Programming for Engineers Matlab Programming for Engineers Matlab Programming for Engineers

Dr. Nidal Farhat

Introduction to MatlabIntroduction to Matlab Matlab Basics Matlab Basics Branching Branching Statements Statements LoopsLoops User Defined Functions User Defined Functions Additional Data Types Additional Data Types Input/Output Functions Input/Output Functions Simulink Toolbox Simulink Toolbox Important Toolboxes (if time is available) Important Toolboxes (if time is available)

Introduction to MatlabIntroduction to Matlab Matlab Basics Matlab Basics Branching Branching Statements Statements LoopsLoops User Defined Functions User Defined Functions Additional Data Types Additional Data Types Input/Output Functions Input/Output Functions Simulink Toolbox Simulink Toolbox Important Toolboxes (if time is available) Important Toolboxes (if time is available)

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OBJECTIVES OBJECTIVES

The while Loop

The for Loop

Logical Arrays and Vectorization

The Matlab Profiler

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THE while LOOPTHE while LOOP

Structure:The Code Block is repeated until the expression is false.

If it is false, the program executes the first statement

after the end.

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Example:

Write a program that calculates the average,

and the standard deviation,

for a set of values (X), entered by the user.

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Solution:

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Solution (modified):

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Solution (modified):

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THE for LOOPTHE for LOOP

Structure:

Repeats a block of statements (Body) specified number of times.

Legal Examples:

Matlab generates an array by evaluating this expression

column by column.

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Legal Examples:

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Example (The Factorial Function):

N! = N * (N-1) * (N-2) * … * 3 * 2 * 1

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Example (The Factorial Function):

N! = N * (N-1) * (N-2) * … * 3 * 2 * 1

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Example, calculating the day of year:

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Example:

Use THE for LOOP to calculate the average and standard deviation for any (n) values (modify the previous while program).

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Details of operation:

1. Indent the bodies of loops (automatically done in Matlab).

2. Don’t modify the loop index within the body of a loop.

3. Preallocating arrays.

recall: arr = 1:4; arr(7) = 8; arr == [1 2 3 4 0 0 8]. (i.e. Matlab automatically extend/change the size of the array.

It is better to preallocate the array before THE for LOOP to make the program much more faster.

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Details of operation: (4. Vectorizing Arrays)

Faster

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The break and continue Statements:

The break statement terminates the execution of a loop and passes control to the next statement after the end of the loop, example:

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The break and continue Statements:

The continue statement terminates the current step of the loop and return the control to the top of the loop, example:

continue

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Nesting Loops:

Output

ii jj product

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Nesting Loops:

Output

ii jj product

Different loop index variables

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Nesting Loops:

The break/continue statements they apply to the current loop, example:

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Logical array and vectorization:

Double array

Logical array

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Logical arrays can serve as a mask for arithmetic operations. The specified operation will be applied to the selected elements and not to the remaining elements, example:

Will take the square root of all elements for which the logical array b is true and leave all the other elements in the array

unchanged

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Example 1:

Calculate the sqrt of all the elements of array (a) > 5.

Faster

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Example 2: Calculate the sqrt of all the elements of array (a) > 5, and the square of the remaining (unselected by the previous operation).

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The Matlab Profiler:

Used to identify the parts of the program that consume most execution time.

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The Matlab Profiler:

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Example: (Projectile Motion)

General equation:

When the ball hits the ground 0

2*0, yvt t

g

0

0

210 2

0

( )

( )

y

x

y t y v t gt

x t x v t

0

0

0

0

sin( )

cos( )

y

x

v v

v v

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Example: (Projectile Motion)

General equation:

When the ball hits the ground 0

2*0, yvt t

g

0

0

210 2

0

( )

( )

y

x

y t y v t gt

x t x v t

0

0

0

0

sin( )

cos( )

y

x

v v

v v

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Example: (Commands and Functions)

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Home WorkHome Work

Solve the following problems:

4.[16, 19, 21]

ch4: loops mechanical engineering department matlab programming for engineers 1 matlab programming...

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