Kursus Matlab di Jakarta Selatan KURSUS MATLAB ONLINE Skripsi, Tesis, DISERTASI 081219449060: KURSUS MATLAB ONLINE Skripsi, Tesis, DISERTASI 081219449060

% Author: Spike

% Date: 11/3/1999

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

lab = input('Please enter the lab mark as a percent [1-100] ');

exam = input('Please enter the exam mark as a percent [1-100] ');

competent = input('Did the student complete all competency exercises [y/n]? ','s');

initialTotal = (lab+exam)/2;

if initialTotal>39

if ~ strncmp(competent,'yes',1)

finalTotal = 39;

elseif lab<40

finalTotal = 39;

elseif exam<40

finalTotal = 39;

else

finalTotal = initialTotal;

end;

else

finalTotal = initialTotal;

end;

fprintf('The final mark for the subject is %5.1f%%\n',finalTotal);

if finalTotal~=initialTotal

fprintf('\t Reset from %5.1f%% due to failure of a component\n',initialTotal);

end;

21.9 SWITCH

• Switch statement used for multiple selection upon a single expression

• Use when can explicitly enumerate the options

• Can always be implemented as an IF-ELSEIF construct

• General form:

switch expression

case test_expression1

statement(s)_1;

case {test_expression2,...,test_expressionN}

statement(s)_2;

case test_expressionM

statement(s)_L;

otherwise

statement(s)_L+1

end;

• Expression must either be a scalar or a string

- equality used for checking if a scalar value

- strcmp() if strings

• First match and corresponding statements executed

• otherwise is catch statement (if no previous match)

21.10 Example –Switch

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% switcher.m

% An example of the use of the Switch-Case

% statement. Converts from one set of units

% of length to a distance in metres.

% Author: Spike

% Date: 11/3/1999

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

disp('UNITS OF DISTANCE CONVERSION PROGRAM');

original = input('Please input the distance [e.g., 7.6] ');

units = input('Please input the units it was measured in ','s');

converted=1;

switch lower(units)

case {'cable','cables'}

metres = original*219.46;

case {'fathom','fathoms'}

metres = original*1.83;

case {'miles','mile','nautical mile','nautical miles'}

metres = original*1852;

otherwise

fprintf('Unknown unit: %s, cannot convert\n',units);

converted=0;

end;

if converted==1

fprintf('%.2f %s is %.2f metres\n',original,units,metres);

end;

21.11 Review

• Motivation for selection statements

• Simple IF

• IF-ELSE

• IF-ELSEIF…

• Nested Ifs

• Truth Tables

• Switch/Case

22 LOOPS IN MATLAB

• Iteration (looping) has a role in all but a handful of all programming languages

- vital to repetitively perform some task

• Iteration falls into two major classes:

definite: a countable number of times

indefinite: until some condition is met

• Today’s lecture considers the implementation of loops in Matlab

- FOR loops

- WHILE loops

- BREAK statement

References: For Engineers (Ch. 1, 7)

Mastering (Ch. 13)

Student (Ch. 11)

22.1 Motivation

• Looping is a vital tool in solving most problems by computer:

- allows the repetition of task without the repetition of code

• Examples include

- standard user-terminated code

repeatedly

obtain user input

perform associated action

until user finished (selected quit option)

- error checking

obtain user input

while input not valid

print warning message

obtain a new input

- repetitive processing of values

for each user supplied value

process current result

get a new value

produce summary/report

22.2 Definite Iteration (FOR Loop)

• Loop a countable number of times

- number of times known at loop initiation, cannot be modified once started

- counter variable takes on new value each time through the loop

- guaranteed termination

• Syntax:

statement_before;

for counter_variable = array

statement(s)_inside;

end;

statement_after;

• For example:

for cnt=1:10

fprintf(‘%d squared=%d\n’,cnt,cnt*cnt);

end;

• <counter_variable> takes on value of each element (column) in array successively

- array tends to be a row vector

- loop executes as many times as there are elements (columns) in the array

22.3 FOR Loop Schematic

22.4 FOR Loop Example

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% forX.m

% An example of the usage of the FOR

% loop to find the mean, max and min

% of a set of numbers.

Kami ada di Jakarta Selatan. KAMI MEMBERIKAN KURSUS MATLAB ONLINE - HUBUNGI MASTER ENGINEERING EXPERT (MEE) 081219449060. Kami membuka kursus Matlab untuk pemula dan mahasiswa atau insinyur yang ingin memperdalam Matlab dan menerapkan dalam bidang teknikal, engineering, rekayasa, dsb. Format bimbingannya tugas-tugas yang bisa membantu Skripsi, Tesis, DISERTASI
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% Note: In matlab this could be done

% without the use of a for loop.

% Author: Spike

% Date: 16/3/1999

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

disp('Program to find the mean, maximum & minimum');

disp('of a sequence of numbers.');

disp(' ');

num = input('Please input the number of values ');

if num>=1

val = input('Please input the first value ');

maxVal = val;

minVal = val;

tally = val;

for cnt = 2:floor(num)

val = input('Please input the next value ');

if val>maxVal

maxVal = val;

elseif val<minVal

minVal = val;

end;

tally = tally + val;

end;

fprintf('Mean=%f, max=%f, min=%f\n',...

tally/num,maxVal,minVal);

else

disp('Must have a positive number of values');

end;

22.5 FOR Loop Additional

• Array is usually a vector created such as 1:n. However consider:

>> A = [1 2 3; 4 5 6]

A =

1 2 3

4 5 6

>> for cnt=A

disp(cnt);

end;

• Note the indentation style

• Modifying the loop counter inside the loop is legal but non-sensical and should not be done

• Loops can be nested:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Creates a dome, peak at (5,5)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

for row=1:10

for column=1:10

height(row,column)=100-((row-5)^2+(column-5)^2);

end;

22.6 Indefinite Iteration (WHILE Loop)

• Loop an indefinite number of times:

- while a boolean condition returns true

- zero through to infinite loop: number of iterations generally unknown at inception

- test evaluated at top of loop

• Syntax:

statement_before;

while test_condition

statement(s)_inside;

end;

statement_after;

• For example:

count = 0;

fprintf(‘Before Loop x=%f, y=%f\n’,…

x,y);

while x<y

x = 5*x^2 – 12.1*x + 27;

y = 2*y;

count = count + 1;

end;

fprintf(‘After %d iterations, x=%f, y=%f\n’,…

count,x,y);

22.7 WHILE Loop Schematic

22.8 WHILE Loop Examples

% Program that loops till user doesn’t require

% anymore.

continue = ‘yes’;

while strnncmp(continue,’y’,1)

x=input(‘Please enter a value ‘);

fprintf(‘f(%f)=%f\n’,x,someFunction(x));

continue = input(‘Would you like to apply the function again [y/n]? ‘,’s’);

end;

% Guard on a user input to ensure it falls

% within a reasonable range.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

velocity=input(‘Please enter a velocity for the aircraft ‘);

while velocity<0 | velocity>10000

disp(‘Only positive velocities up to 10,000 km/hr accepted’);

velocity=input(‘Please enter an acceptable velocity for the aircraft ‘);

end;

% Loops to build a vector who’s elements

% monotonically increase by pi/8 until cosine

% returns a negative value. Note there is no

% need to check all elements of the vector, but

% for illustration purposes that is what is

% happening each time at the top of the loop

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

vec(1) = 0;

while cos(vec)>=0

vec(end+1)=vec(end)+pi/8;

end;

disp(‘Final vector is:’);

disp(vec);

22.9 WHILE vs IF

• It is important to appreciate the differences between IF & WHILE and employ the correct structure in the correct circumstances:

- IF executes the code once (if the condition is true) & continues with execution

- WHILE continues to execute the code between the WHILE & END statements until the condition becomes false.

22.10 General Loops & BREAK

• Matlab provides the break statement to allow exit from a loop at an arbitrary location

• An infinite loop may be written easily by employing a WHILE loop with a boolean condition that is always true

- In Matlab the value 1 is treated as true, while 0 is false

while 1

disp(‘An infinite loop. Hit <cntrl>-C to kill’);

end;

• Combining the above two facts allows for loops which exit at any place

while 1

velocity=input(‘Please enter an aircraft velocity [1-10,000] ‘);

if velocity>0 & velocity<=10000

break;

end; % IF

disp(‘Unacceptable velocity for the plane.’);

end; % WHILE

22.11 Break Schematic

statement_before;

while test

statement(s)_1;

if exit_condition

break;

end;

statement(s)_2;

end;

statement_after;

22.12 Combined (Major) Example

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% worms.m

% A simple script file to calculate where a

% shell will land when the landscape is not

% flat. Users input initial statistics for the

% shell and also how large (in metres) the 1D

% terrain is. The terrain is randomly generated

% then a loop employed to track the shell at

% intervals of 0.1 seconds until it hits the

% ground or goes out of range of the terrain

% generated.

% Author: Spike

% Date: 17/3/1999

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%

% Grab the terrain size

%%%%%%%%%%%%%%%%%%%%%%%%%%

while 1

length=input('Please input the length of the landscape in metres ');

if length>0

length=ceil(length);

break;

end;

disp('Sorry, length must be positive');

end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Plot the intial Terrain

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

terrain = makeTerrain(length);

plot(terrain);

xlabel('Horizontal Distance (metres)');

ylabel('Height (metres)');

title('Shell Shot on Variable Terrain');

Example (Cont)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Safe input of muzzle velocity

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

while 1

muzzle=input('Please provide the muzzle velocity in metres/sec ');

if muzzle>0

break;

end;

disp('Sorry, must be a positive velocity');

end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Safe input of barrel's inclination

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

while 1

incline=input('Please input the angle of the barrel relative to the horizon ');

if incline>0 & incline<180

break;

end;

disp('Angle must be between 0 and 180 degrees');

end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Set up constants and explicitly handle the

% very first tenth of a second.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

timeStep = 0.1; % Snapshot 10 times per sec

gravity=9.8; % Acceleration due to gravity

currentTime=0.1; % Current elapsed time since shot fired

initialHeight=1.0; % Height of barrel above ground.

xDelta=muzzle*cos(incline*pi/180)*timeStep;

% Constant horizontal

% movement per timeStep

Example (Cont)

yVelocity=muzzle*sin(incline*pi/18

% Velocity in y direction.

xloc=1+xDelta;

% Horizontal location of shell

yloc=terrain(1)+initialHeight+yVelocity…

*currentTime-0.5*gravity*currentTime^2;

% Vertical location of shell

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Main loop. While we haven't run off the end of

% the terrain in either direction. Check to see

% if we have hit the ground. If not advance time

% by 1/10th % of a sec and find the shell's new

% co-ordinates.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

while round(xloc)>=1 & round(xloc)<=length

if yloc<terrain(round(xloc)) % HIT the ground!

text(xloc,terrain(round(xloc)),'Bang');

% mark on the map

break; % Quit loop

end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Advance time and find new co-ordinates

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

currentTime=currentTime+timeStep;

xloc=xloc+xDelta;

yloc=terrain(1)+initialHeight+yVelocity*currentTime-0.5*gravity*currentTime^2;

end;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Finished loop. Hence shell either hit ground

% or flew off edge of the map. Determine which

% and print an appropriate message

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if round(xloc)>=1 & round(xloc)<=length

fprintf('At %5.1f seconds the shell impacted at co-ordinates (%5.1f,%5.1f)\n',currentTime,xloc,yloc);

else

fprintf('At %5.1f the shell was at (%5.1f,%5.1f) and left the terrain\n',currentTime,xloc,yloc);

end;

22.13 Worms Run

>> worms

Please input the length of the landscape in metres 1000

Please provide the muzzle velocity in metres/sec 100

Please input the angle of the barrel relative to the horizon 60

At 17.5 seconds the shell impacted at co-ordinates (876.0, 15.9)

>> diary off

22.14 Loop Usage Guidelines

• Should use most appropriate loop construct for the particular problem at hand

while loop

- most general form of loop

- use for indefinite iteration

- can control number of executions by appropriate execution

- generally easy to read/understand

for loop

- used for definite iteration

- easy to read

- can always be implemented as a while loop

break & general loop

- should generally be avoided (preferentially employ while)

- use if structure of problem demands such

- often hard to read/understand (multiple exits)

22.15 Loop Control

• three aspects to loop control for any loop:

• Initialisation of loop parameter(s)

- automatic in a FOR loop

- before a WHILE loop

- before a general loop or before the exit test

• Test

- automatic in a FOR loop

- WHILE: test for continuation

- GENERAL: test for termination

• Update loop parameter

- non-sensical in FOR loop

- must update in GENERAL & WHILE loops

22.16 Common Types of Loops

• Certain styles of loop construct are used repetitively due to their utility:

Sentinel Guarded

- used when an unknown number of items are to be entered

- select a special value which the user employs to indicate end-of-data

+ obviously special value should not be a feasible input for processing

sentinel = -1;

val=input(‘Please enter a positive value [-1 to exit]’);

while val~=sentinel

sum = sum+val;

val=input(‘Please enter a positive value [-1 to exit]’);

end;

Flag Guarded

- employ a boolean flag (variable) to indicate termination

finished=0; % Our flag set to false

while ~finished

if <desired event has happened>

finished=1;

end;

22.17 Loops vs Implicit Vectorisation

• In most programming languages loops are used to:

- iteratively process items (e.g., array contents)

- produce tables & charts

• Due to Matlab’s implicit vectorisation loops are often unnecessary

- operations applied to entire arrays in one statement

- vectorised I/O

• Lecture on efficiency covers the issue in more detail

• Consider the example used at the start of the lecture to illustrate FOR loops:

22.18 Loops vs. Vector Example

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% forX_alt.m

% An alternative to the FOR loop

% example showing Matlab's support

% for implicit vectorisation and hence

% that there is often no need for

% explicit looping.

% Date: 16/3/1999

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

disp('Program to find the mean, maximum & minimum');

disp('of a sequence of numbers.');

disp(' ');

num = input('Please input the number of values ');

if num>=1

disp('Please input the values now ');

values = input('enclosed by square brackets- e.g., [1 67 87.4] ');

fprintf('Mean=%f, max=%f, min=%f\n',...

Kursus Matlab di Jakarta Selatan KURSUS MATLAB ONLINE Skripsi, Tesis, DISERTASI 081219449060

Selasa, 13 Januari 2015

KURSUS MATLAB ONLINE Skripsi, Tesis, DISERTASI 081219449060

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