MATLAB QUICK REFERENCE
Arrays, matrices, plotting, file I/O, control flow
Basics
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
Help & Info
help sin % quick help for function
doc sin % open documentation
who % list variables in workspace
whos % list with details (size, type)
Operators
| + - * / ^ | Arithmetic (matrix operations) |
| .* ./ .^ | Element-wise operations |
| == ~= < > <= >= | Comparison operators |
| && || ~ | Logical AND, OR, NOT (scalars) |
| & | ~ | Element-wise logical (arrays) |
Variables & Types
Numeric Types
x = 3.14; % double (default)
n = int32(42); % 32-bit integer
z = 2 + 3i; % complex number
tf = true; % logical
Type Checking
| class(x) | Return type name as string |
| isa(x, 'double') | Check if x is specific type |
| isnumeric(x) | True if numeric type |
| ischar(x) | True if character array |
| islogical(x) | True if logical type |
Special Constants
| pi | 3.14159... |
| Inf / -Inf | Infinity |
| NaN | Not a Number |
| eps | Machine epsilon (~2.2e-16) |
| i / j | Imaginary unit |
Arrays & Matrices
Creating Arrays
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]
Built-in Constructors
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]
Indexing & 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
Matrix Operations
| A' | Transpose (conjugate) |
| A.' | Transpose (no conjugate) |
| inv(A) | Matrix inverse |
| det(A) | Determinant |
| eig(A) | Eigenvalues and eigenvectors |
| A \ b | Solve Ax = b |
| size(A) | Dimensions [rows cols] |
| numel(A) | Total number of elements |
Control Flow
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
Loop Control
| break | Exit the innermost loop |
| continue | Skip to next iteration |
| return | Exit function immediately |
Functions
Function File
% Save as myfunc.m
function result = myfunc(x, y)
result = x.^2 + y.^2;
end
Multiple Outputs
function [mn, mx] = minmax(v)
mn = min(v);
mx = max(v);
end
[lo, hi] = minmax([3 1 4 1 5]);
Anonymous Functions
f = @(x) x.^2 + 1;
f(3) % returns 10
g = @(x,y) x + y;
arrayfun(f, [1 2 3]) % apply to each element
Useful Built-ins
| sum(v) | Sum of elements |
| mean(v) | Mean value |
| max(v) / min(v) | Maximum / minimum |
| sort(v) | Sort ascending |
| find(v > 3) | Indices where condition is true |
| length(v) | Length of vector |
Plotting
2D Plots
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)')
Multiple Plots
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))
Other Plot Types
| bar(x, y) | Bar chart |
| histogram(data) | Histogram |
| scatter(x, y) | Scatter plot |
| pie(data) | Pie chart |
| surf(X, Y, Z) | 3D surface plot |
| imagesc(A) | Display matrix as image |
Save Figure
saveas(gcf, 'plot.png')
exportgraphics(gcf, 'plot.pdf')
File I/O
Text Files
data = readmatrix('data.csv');
writematrix(A, 'output.csv')
T = readtable('data.csv');
writetable(T, 'output.csv')
MAT Files
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
Low-Level File I/O
fid = fopen('log.txt', 'w');
fprintf(fid, 'Value: %f\n', 3.14);
fclose(fid);
lines = readlines('log.txt');
String Operations
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)
String Functions
| strlength(s) | Length of string |
| upper(s) / lower(s) | Case conversion |
| contains(s, pat) | True if pattern found |
| replace(s, old, new) | Replace substring |
| split(s, delim) | Split into array |
| join(arr, delim) | Join string array |
| strip(s) | Remove leading/trailing whitespace |
Formatting
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 Arrays
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
Structs
s.name = 'Alice';
s.age = 30;
s.scores = [90 85 92];
fieldnames(s) % {'name','age','scores'}
rmfield(s, 'age') % remove field
Struct Arrays
people(1).name = 'Alice'; people(1).age = 30;
people(2).name = 'Bob'; people(2).age = 25;
{people.name} % {'Alice', 'Bob'}
[people.age] % [30, 25]
Common Patterns
Vectorized Operations
% Avoid loops — use vectorization
v = 1:1000;
result = sum(v.^2); % fast
idx = v(v > 500 & v < 600); % logical indexing
Table Operations
T = table([25;30], ["A";"B"], 'VariableNames', ...
{'Age','Grade'});
T.Age % access column
T(T.Age > 25, :) % filter rows
Error Handling
try
result = riskyFunction(x);
catch ME
fprintf('Error: %s\n', ME.message);
end
Timing Code
tic
heavyComputation();
toc % prints elapsed time