MATLAB Basics: Environment, Commands, Plotting & Tips

Posted on Jan 28, 2026 in Computers

🖥️ 1. MATLAB Basics & Environment

MATLAB = Matrix Laboratory — a numerical computing environment and programming language built for engineering and mathematical operations.

🔹 Interface Overview

Prompt symbol: >>
Comment: %
Suppress output: ;
Continue line: ...

🔹 Core Commands

🔹 Scripting & Execution

Script: a series of commands saved in a .m file.
Run by typing the filename (without .m).

Example Script:

% Circle area calculation
r = 5;
A = pi * r^2;
fprintf('Area = %.2f\n', A)

🧩 2. Variables, Arrays & Operations

🔹 Variable Rules

• Must start with a letter.
• Case sensitive.
• Cannot contain spaces.
• Assign using =.

Examples:

x = 5;
y = 3.14;
z = 'hello';

🔹 Arrays & Matrices

Row vector: v = [1 2 3 4]
Column vector: v = [1; 2; 3; 4]
Matrix:

A = [1 2 3;
     4 5 6;
     7 8 9];

🔹 Array Generation Functions

🔹 Colon Operator

Creates ranges:

v = 1:2:10   % [1 3 5 7 9]

Row → column: v'
Every k-th element: v(1:3:end)

Example (Lab 2):

v = 5:5:50;    % row vector
v = v';        % column vector
v(1:3:end)

🔹 Subarrays & Indexing

A(r1:r2, c1:c2) extracts a submatrix.
A(:,2) → entire 2nd column.
A(3,:) → entire 3rd row.
A(2,:) = 0 → replace row with zeros.
end keyword = last index.

Example (Lab 2):

B = [2 4 6 8;
     1 3 5 7;
     9 11 13 15];
B(:, [1 end])   % first and last columns
B(2,:) = 0;

🔹 Arithmetic Operators

Order of operations:
() → ^ → *// → +/-.

🔹 Built-in Math Functions

🔹 Display & Formatting

Example (Lab 2):

temp = 37.4567;
disp(temp)
fprintf('The temperature is %.1f°C\n', temp)

🔹 Special Constants

pi, i/j, Inf, NaN, eps, date, clock, ans.

Example (Lab 2):

1/0     % Inf
Inf-Inf % NaN

📊 3. Plotting & Visualization

🔹 Basic Plotting

x = 0:0.1:10;
y = sin(x);
plot(x,y,'r--o','LineWidth',1.5)
xlabel('x'); ylabel('sin(x)');
title('Sine Wave'); grid on

Multiple plots:

hold on
plot(x,cos(x),'b')
legend('sin(x)','cos(x)')
hold off

Axis commands:
axis equal, axis tight, axis square, axis off.

Subplots:

subplot(2,1,1); plot(x,sin(x));
subplot(2,1,2); plot(x,cos(x));
sgtitle('Sine vs Cosine')

🔹 Logarithmic Plots

🔹 Specialized Plots

🔹 Line Styles & Markers

🔹 Annotating Plots

text(12,25,'Midday Peak')
annotation('textbox',[.5 .5 .1 .1],'String','Note')

🔹 Lab Examples

Lab 3 – Weather Dashboard:

t=0:1:24;
T=18+7*sin(pi*(t-6)/12);
H=60+15*cos(pi*t/12);
yyaxis left; plot(t,T,'r--o');
yyaxis right; plot(t,H,'b');
title('Daily Weather'); grid on

Lab 3 – Elevator Motion:

stairs(tStops,floors);
hold on; stem(tStops,floors);
bar(floors(2:end),dwell);

Lab 3 – Wind Snapshot:

theta=dirDeg*pi/180;
polarplot(theta,spd,'o-');
u=spd.*cos(theta); v=spd.*sin(theta);
compass(u,v);

⚙️ 4. Logicals, Branching & Design

🔹 Relational Operators

==, ~=, <, >, <=, >=.

🔹 Logical Operators

&, |, ~, &&, ||, xor(a,b).

🔹 if / elseif / else

if temp>35
 disp('Too hot')
elseif temp<15
 disp('Too cold')
else
 disp('Safe')
end

🔹 switch / case

switch choice
 case 1, A=pi*r^2;
 case 2, A=L*W;
 case 3, A=0.5*b*h;
 otherwise, disp('Invalid')
end

🔹 try / catch

try
 riskyOp
catch
 disp('Error handled')
end

🔹 Lab Examples

Lab 4 – Temperature Safety:

temp = input('Enter temperature: ');
if (temp>=15)&&(temp<=35)
 disp('Safe to operate')
elseif temp<15
 disp('Too cold')
else
 disp('Too hot')
end

Lab 4 – Grading System:

score=input('Enter score: ');
if score>=90
 disp('A')
elseif score>=80
 disp('B')
elseif score>=70
 disp('C')
elseif score>=60
 disp('D')
else
 disp('F')
end

🔁 5. Loops & Iteration

🔹 while-loop

temp=51; t=0;
while temp>35 && t<120
 fprintf('t=%d min: %.1f°C\n',t,temp)
 temp=temp-3.5; t=t+1;
end
if temp<=35
 disp('SAFE')
else
 disp('ALERT')
end

🔹 for-loop

steps=[5600 7200 6800 8000 9100 4500 10200];
total=0; maxSteps=0;
for i=1:length(steps)
 total=total+steps(i);
 if steps(i)>maxSteps
  maxSteps=steps(i); day=i;
 end
end
avg=total/length(steps);
fprintf('Total=%d Avg=%.1f MaxDay=%d\n',total,avg,day)

🔹 continue / break

tx=[45 52 -1 39 99999 28];
sum=0;
for k=1:length(tx)
 if tx(k)<0, fprintf('Skip %d\n',tx(k)); continue; end
 if tx(k)==99999, fprintf('FRAUD FLAG at %d\n',k); break; end
 sum=sum+tx(k);
end

🧮 6. Functions

🔹 Basic Function Structure

function out = funcName(inputs)
% Description (H1 line)
out = expression;
end

🔹 Example (Lab 6)

function Rt = series_resistance(R1,R2)
Rt = R1 + R2;
end

🔹 Pass-by-Value

Variables inside functions do not affect originals outside.

🔹 Optional Inputs / Outputs

function [avg,stdev]=temp_analysis(data,unit)
narginchk(1,2)
if nargin==1, unit='C'; end
if unit=='F', data=(data-32)*5/9; end
if ~isnumeric(data), error('Must be numeric'); end
avg=mean(data);
if nargout>1, stdev=std(data); end
end

🔹 Persistent Variable

function total = alert_counter(value)
persistent count
if isempty(count), count=0; end
if nargin==0, total=count; return; end
if ischar(value)&&strcmp(value,'reset')
 count=0;
else
 count=count+value;
end
total=count;
end

⚡ 7. Formulas, Shortcuts, and Hints

⚙️ Debugging

• Breakpoints: click the red dot in the Editor.
• Step In/Over/Out: trace code execution.
• Pause on Errors: automatically stop on errors.
• Common Errors:
  • Syntax: missing end or ).
  • Runtime: invalid index, division by zero.
  • Logic: incorrect calculation.

🧠 Helpful Tips

• Use ; to suppress output.
• Use format long for increased decimal precision.
• Always check vector and matrix sizes before multiplying.
• Comment often with %.
• Preallocate arrays for loops (improves speed).
• Use help anytime for documentation.

Would you like me to continue this reference to include:

• More lab-specific “Expected Answer” outputs and formulas

• Extra notes on function handles, input/output, debugging tools, and plotting formatting (color, grid, axis labels, etc.)

It would add another 4–5 pages worth of information, still as text.
Do you want me to keep going?