dasar komputer-user defined function.ppt

7/27/2019 Dasar Komputer-User defined function.ppt

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© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

ITE PC v4.0

Chapter 9 1

User Defined Function



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Chapter 9 2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public

MATLAB Function

A special type of M-file that runs in its own

independent workspace. Receives input data through an input argument list Return results to the caller through an output

argument l ist

Bentuk dasar MATLAB function

Function [outarg1, outarg2,…]=fname(inarg1, inarg2, …) % H1 comment line....(Executable code)

....(return)(end)

MATLAB function should be place in a file with thesame name as the function and the file extension is“.m”



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Built-in-Function

Beberapa fungsi matematika yang dapat kita gunakan

untuk operasi matematika antara lain sebagai berikut:

abs(x) : untuk menghasilkan nilai absolut dari x sign(x) : untuk menghasilkan nilai -1 jika x<0, 0 jika x=0 dan

1 jika x>1 exp(x) : untuk menghasilkan nilai eksponensian natural, e x

log(x) : untuk menghasilkan nilai logaritma natural x, ln x

log10(x) : untuk menghasilkan nilai logaritma dengan basis 10, x 10 log

sqrt(x) : untuk menghasilkan akar dari nilai x, x rem(x,y) : untuk menghasilkan nilai modulus (sisa pembagian)

x terhadap y

Untuk selengkapnya fungsi-fungsi lain dapat ditemukan

pada buku-buku teks mengenai MATLAB



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Di dalam M File, kita dapat menuliskan fungsi-fungsi

yang berisikan berbagai operasi sehingga menghasilkandata yang diinginkan.

Bentuk penulisan nama fungsi:

Contoh:



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Fungsi yang dibuat bernama „testfungsi‟ memiliki tiga

nilai masukan „c,d,e‟ dan dua nilai keluaran „a,b‟ Selanjutnya fungsi tersebut akan dijalankan melalui

command window dengan nilai masukan ‟10,2,4‟. Perhatikan penulisan kurung siku „[ ]‟ pada nilai keluaran

dan kurung biasa„( )‟ pada nilai masukan.




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User Defined Functionfunction distance = dist2 (x1, y1, x2, y2)%DIST2 Calculate the distance between two points

% Function DIST2 calculates the distance betwee% two points (x1,y1) and (x2,y2) in a cartesian% coordinate system%% Calling sequence:% distance = dist2(x1, y1, x2, y2)% Define variables:% x1 -- absisca position of point 1% y1 -- ordinate position of point 1% x2 -- absisca position of point 2% y2 -- ordinate position of point 2% distance -- Distance between the two points

% Record of revision% Date Programmer Descripotion of Change% ==== ========== ======================% 04/12/08 Harinaldi Original code

% Calculate distancedistance = sqrt((x2-x1).^2 + (y2-y1).^2);


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Function Caller Script% Script file: test_dist2.m%% Purpose:

% This program tests function dist2%% Record of revisions:% Date Programmer Description of change% 04/12/08 Harinaldi Original code%% Define variables:% xA -- absisca position of point A% yA -- ordinate position of point A% xB -- absisca position of point B% yB -- ordinate position of point B% result -- Distance between the points

% Get input datadisp ('Calculate the distance between two points: ');

xA = input ('Enter absisca of point A (xA): ');yA = input ('Enter ordinate of point A (yA): ');xB = input ('Enter absisca of point B (xB): ');yB = input ('Enter ordinate of point B (yB): ');

% Evaluation functionresult = dist2 (xA, yA, xB, yB);

% Write out resultfprintf('The distance between point A and B is %f\n', result);




Results

>> test_dist2Calculate the distance between two points:

Enter absisca of point A (xA): 1Enter ordinate of point A (yA): 3Enter absisca of point B (xB): 2Enter ordinate of point B (yB): 4The distance between point A and B is 1.414214




Variable Passing: Pass-By-Value MATLAB programs communicate with their function

using a pass-by-value scheme When a function call occurs, MATLAB makes copy

of the actual argument and passes them to the function Even if the function modifies the input arguments, it

will not affects the original data in the caller



Chapter 9 10© 2007 Cisco Systems Inc All rights reserved Cisco Public

Variable Passing: Pass-By-Value

function out = sample (a, b)fprintf('Inside sample: a = %f, b = %f %f\n', a, b);

a = b(1)+ 2*a;b = a .* b;out = a + b(1);fprintf('Inside sample: a = %f, b = %f %f\n', a, b);

% Script : test_samplea = 2; b = [6 4];fprintf('Before sample: a = %f, b = %f %f\n', a, b);c = sample(a,b);fprintf('After sample: a = %f, b = %f %f\n', a, b);fprintf('After sample: c = %f\n', c);

>> test_sampleBefore sample: a = 2.000000, b = 6.000000 4.000000Inside sample: a = 2.000000, b = 6.000000 4.000000Inside sample: a = 10.000000, b = 60.000000 40.000000

After sample: a = 2.000000, b = 6.000000 4.000000After sample: c = 70.000000

dasar komputer-user defined function.ppt

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