REFERENSI CEPAT MATLAB
Array, matriks, plotting, I/O file, alur kontrol
Dasar
Command Window
x = 5; % assign (semicolon suppresses output)
x = 5 % assign and display result
disp('Hello') % print to console
clc % clear command window
clear % clear all variables
Bantuan & Info
help sin % quick help for function
doc sin % open documentation
who % list variables in workspace
whos % list with details (size, type)
Operator
| + - * / ^ | Aritmatika (operasi matriks) |
| .* ./ .^ | Operasi element-wise |
| == ~= < > <= >= | Operator perbandingan |
| && || ~ | AND, OR, NOT logika (skalar) |
| & | ~ | Logika element-wise (array) |
Variabel & Tipe
Tipe Numerik
x = 3.14; % double (default)
n = int32(42); % 32-bit integer
z = 2 + 3i; % complex number
tf = true; % logical
Pemeriksaan Tipe
| class(x) | Kembalikan nama tipe sebagai string |
| isa(x, 'double') | Periksa apakah x adalah tipe tertentu |
| isnumeric(x) | True jika tipe numerik |
| ischar(x) | True jika array karakter |
| islogical(x) | True jika tipe logika |
Konstanta Khusus
| pi | 3.14159... |
| Inf / -Inf | Tak hingga |
| NaN | Bukan Angka |
| eps | Epsilon mesin (~2.2e-16) |
| i / j | Satuan imajiner |
Array & Matriks
Membuat Array
v = [1 2 3 4 5]; % row vector
v = [1; 2; 3]; % column vector
A = [1 2; 3 4]; % 2x2 matrix
r = 1:5; % [1 2 3 4 5]
r = 0:0.5:2; % [0 0.5 1 1.5 2]
Konstruktor Bawaan
zeros(3) % 3x3 of zeros
ones(2, 4) % 2x4 of ones
eye(3) % 3x3 identity
rand(2, 3) % 2x3 uniform random
linspace(0,1,5) % 5 evenly spaced [0..1]
Pengindeksan & Slicing
A(2, 3) % row 2, col 3
A(1, :) % entire first row
A(:, 2) % entire second column
A(1:2, 1:2) % submatrix
A(end, :) % last row
Operasi Matriks
| A' | Transpos (konjugat) |
| A.' | Transpos (tanpa konjugat) |
| inv(A) | Invers matriks |
| det(A) | Determinan |
| eig(A) | Nilai eigen dan vektor eigen |
| A \ b | Selesaikan Ax = b |
| size(A) | Dimensi [baris kolom] |
| numel(A) | Jumlah total elemen |
Alur Kontrol
if / elseif / else
if x > 0
disp('positive')
elseif x == 0
disp('zero')
else
disp('negative')
end
for & while
for i = 1:10
fprintf('i = %d\n', i);
end
while x > 0
x = x - 1;
end
switch
switch grade
case 'A'
disp('Excellent')
case {'B', 'C'}
disp('Good')
otherwise
disp('Try harder')
end
Kontrol Perulangan
| break | Keluar dari perulangan terdalam |
| continue | Lanjut ke iterasi berikutnya |
| return | Keluar dari fungsi segera |
Fungsi
File Fungsi
% Save as myfunc.m
function result = myfunc(x, y)
result = x.^2 + y.^2;
end
Beberapa Output
function [mn, mx] = minmax(v)
mn = min(v);
mx = max(v);
end
[lo, hi] = minmax([3 1 4 1 5]);
Fungsi Anonim
f = @(x) x.^2 + 1;
f(3) % returns 10
g = @(x,y) x + y;
arrayfun(f, [1 2 3]) % apply to each element
Built-in Berguna
| sum(v) | Jumlah elemen |
| mean(v) | Nilai rata-rata |
| max(v) / min(v) | Maksimum / minimum |
| sort(v) | Urutkan naik |
| find(v > 3) | Indeks di mana kondisi benar |
| length(v) | Panjang vektor |
Plotting
Plot 2D
x = 0:0.1:2*pi;
plot(x, sin(x), 'r-', 'LineWidth', 2)
xlabel('x'); ylabel('sin(x)')
title('Sine Wave'); grid on
legend('sin(x)')
Plot Ganda
hold on
plot(x, sin(x), 'b-')
plot(x, cos(x), 'r--')
hold off
subplot(1,2,1); plot(x, sin(x))
subplot(1,2,2); plot(x, cos(x))
Tipe Plot Lain
| bar(x, y) | Diagram batang |
| histogram(data) | Histogram |
| scatter(x, y) | Plot sebar |
| pie(data) | Diagram lingkaran |
| surf(X, Y, Z) | Plot permukaan 3D |
| imagesc(A) | Tampilkan matriks sebagai gambar |
Simpan Gambar
saveas(gcf, 'plot.png')
exportgraphics(gcf, 'plot.pdf')
I/O File
File Teks
data = readmatrix('data.csv');
writematrix(A, 'output.csv')
T = readtable('data.csv');
writetable(T, 'output.csv')
File MAT
save('workspace.mat') % save all variables
save('data.mat', 'x', 'y') % save specific vars
load('data.mat') % load into workspace
S = load('data.mat'); % load into struct
I/O File Level Rendah
fid = fopen('log.txt', 'w');
fprintf(fid, 'Value: %f\n', 3.14);
fclose(fid);
lines = readlines('log.txt');
Operasi String
String vs Char Array
s = "Hello"; % string (double quotes)
c = 'Hello'; % char array (single quotes)
s + " World" % "Hello World" (string)
[c, ' World'] % 'Hello World' (char concat)
Fungsi String
| strlength(s) | Panjang string |
| upper(s) / lower(s) | Konversi huruf |
| contains(s, pat) | True jika pola ditemukan |
| replace(s, old, new) | Ganti substring |
| split(s, delim) | Pisahkan menjadi array |
| join(arr, delim) | Gabungkan array string |
| strip(s) | Hapus spasi di awal/akhir |
Pemformatan
sprintf('x = %.2f', 3.14159) % "x = 3.14"
fprintf('i = %d\n', 42) % print to console
num2str(3.14) % number to string
str2double("3.14") % string to number
Cell & Struct
Cell Array
C = {1, 'hello', [1 2 3]}; % mixed types
C{2} % access: 'hello'
C{end+1} = true; % append element
cellfun(@length, C) % apply func to each
Struct
s.name = 'Alice';
s.age = 30;
s.scores = [90 85 92];
fieldnames(s) % {'name','age','scores'}
rmfield(s, 'age') % remove field
Array Struct
people(1).name = 'Alice'; people(1).age = 30;
people(2).name = 'Bob'; people(2).age = 25;
{people.name} % {'Alice', 'Bob'}
[people.age] % [30, 25]
Pola Umum
Operasi Vektorisasi
% Avoid loops — use vectorization
v = 1:1000;
result = sum(v.^2); % fast
idx = v(v > 500 & v < 600); % logical indexing
Operasi Tabel
T = table([25;30], ["A";"B"], 'VariableNames', ...
{'Age','Grade'});
T.Age % access column
T(T.Age > 25, :) % filter rows
Penanganan Error
try
result = riskyFunction(x);
catch ME
fprintf('Error: %s\n', ME.message);
end
Mengukur Waktu
tic
heavyComputation();
toc % prints elapsed time