matlab

---

name: matlab description: MATLAB and GNU Octave numerical computing for matrix operations, data analysis, visualization, and scientific computing. Use when writing MATLAB/Octave scripts for linear algebra, signal processing, image processing, differential equations, optimization, statistics, or creating scientific visualizations. Also use when the user needs help with MATLAB syntax, functions, or wants to convert between MATLAB and Python code. Scripts can be executed with MATLAB or the open-source GNU Octave interpreter. license: For MATLAB (https://www.mathworks.com/pricing-licensing.html) and for Octave (GNU General Public License version 3) compatibility: Requires either MATLAB or Octave to be installed for testing, but not required for just generating scripts. metadata: {"version": "1.0", "skill-author": "K-Dense Inc."}

MATLAB/Octave Scientific Computing

MATLAB is a numerical computing environment optimized for matrix operations and scientific computing. GNU Octave is a free, open-source alternative with high MATLAB compatibility.

Quick Start

Running MATLAB scripts:

# MATLAB (commercial)
matlab -nodisplay -nosplash -r "run('script.m'); exit;"

# GNU Octave (free, open-source)
octave script.m

Install GNU Octave:

# macOS
brew install octave

# Ubuntu/Debian
sudo apt install octave

# Windows - download from https://octave.org/download

Core Capabilities

1. Matrix Operations

MATLAB operates fundamentally on matrices and arrays:

% Create matrices
A = [1 2 3; 4 5 6; 7 8 9];  % 3x3 matrix
v = 1:10;                     % Row vector 1 to 10
v = linspace(0, 1, 100);      % 100 points from 0 to 1

% Special matrices
I = eye(3);          % Identity matrix
Z = zeros(3, 4);     % 3x4 zero matrix
O = ones(2, 3);      % 2x3 ones matrix
R = rand(3, 3);      % Random uniform
N = randn(3, 3);     % Random normal

% Matrix operations
B = A';              % Transpose
C = A * B;           % Matrix multiplication
D = A .* B;          % Element-wise multiplication
E = A \ b;           % Solve linear system Ax = b
F = inv(A);          % Matrix inverse

For complete matrix operations, see references/matrices-arrays.md.

2. Linear Algebra

% Eigenvalues and eigenvectors
[V, D] = eig(A);     % V: eigenvectors, D: diagonal eigenvalues

% Singular value decomposition
[U, S, V] = svd(A);

% Matrix decompositions
[L, U] = lu(A);      % LU decomposition
[Q, R] = qr(A);      % QR decomposition
R = chol(A);         % Cholesky (symmetric positive definite)

% Solve linear systems
x = A \ b;           % Preferred method
x = linsolve(A, b);  % With options
x = inv(A) * b;      % Less efficient

For comprehensive linear algebra, see references/mathematics.md.

3. Plotting and Visualization

% 2D Plots
x = 0:0.1:2*pi;
y = sin(x);
plot(x, y, 'b-', 'LineWidth', 2);
xlabel('x'); ylabel('sin(x)');
title('Sine Wave');
grid on;

% Multiple plots
hold on;
plot(x, cos(x), 'r--');
legend('sin', 'cos');
hold off;

% 3D Surface
[X, Y] = meshgrid(-2:0.1:2, -2:0.1:2);
Z = X.^2 + Y.^2;
surf(X, Y, Z);
colorbar;

% Save figures
saveas(gcf, 'plot.png');
print('-dpdf', 'plot.pdf');

For complete visualization guide, see references/graphics-visualization.md.

4. Data Import/Export

% Read tabular data
T = readtable('data.csv');
M = readmatrix('data.csv');

% Write data
writetable(T, 'output.csv');
writematrix(M, 'output.csv');

% MAT files (MATLAB native)
save('data.mat', 'A', 'B', 'C');  % Save variables
load('data.mat');                   % Load all
S = load('data.mat', 'A');         % Load specific

% Images
img = imread('image.png');
imwrite(img, 'output.jpg');

For complete I/O guide, see references/data-import-export.md.

5. Control Flow and Functions

% Conditionals
if x > 0
    disp('positive');
elseif x < 0
    disp('negative');
else
    disp('zero');
end

% Loops
for i = 1:10
    disp(i);
end

while x > 0
    x = x - 1;
end

% Functions (in separate .m file or same file)
function y = myfunction(x, n)
    y = x.^n;
end

% Anonymous functions
f = @(x) x.^2 + 2*x + 1;
result = f(5);  % 36

For complete programming guide, see references/programming.md.

6. Statistics and Data Analysis

% Descriptive statistics
m = mean(data);
s = std(data);
v = var(data);
med = median(data);
[minVal, minIdx] = min(data);
[maxVal, maxIdx] = max(data);

% Correlation
R = corrcoef(X, Y);
C = cov(X, Y);

% Linear regression
p = polyfit(x, y, 1);  % Linear fit
y_fit = polyval(p, x);

% Moving statistics
y_smooth = movmean(y, 5);  % 5-point moving average

For statistics reference, see references/mathematics.md.

7. Differential Equations

% ODE solving
% dy/dt = -2y, y(0) = 1
f = @(t, y) -2*y;
[t, y] = ode45(f, [0 5], 1);
plot(t, y);

% Higher-order: y'' + 2y' + y = 0
% Convert to system: y1' = y2, y2' = -2*y2 - y1
f = @(t, y) [y(2); -2*y(2) - y(1)];
[t, y] = ode45(f, [0 10], [1; 0]);

For ODE solvers guide, see references/mathematics.md.

8. Signal Processing

% FFT
Y = fft(signal);
f = (0:length(Y)-1) * fs / length(Y);
plot(f, abs(Y));

% Filtering
b = fir1(50, 0.3);           % FIR filter design
y_filtered = filter(b, 1, signal);

% Convolution
y = conv(x, h, 'same');

For signal processing, see references/mathematics.md.

Common Patterns

Pattern 1: Data Analysis Pipeline

% Load data
data = readtable('experiment.csv');

% Clean data
data = rmmissing(data);  % Remove missing values

% Analyze
grouped = groupsummary(data, 'Category', 'mean', 'Value');

% Visualize
figure;
bar(grouped.Category, grouped.mean_Value);
xlabel('Category'); ylabel('Mean Value');
title('Results by Category');

% Save
writetable(grouped, 'results.csv');
saveas(gcf, 'results.png');

Pattern 2: Numerical Simulation

% Parameters
L = 1; N = 100; T = 10; dt = 0.01;
x = linspace(0, L, N);
dx = x(2) - x(1);

% Initial condition
u = sin(pi * x);

% Time stepping (heat equation)
for t = 0:dt:T
    u_new = u;
    for i = 2:N-1
        u_new(i) = u(i) + dt/(dx^2) * (u(i+1) - 2*u(i) + u(i-1));
    end
    u = u_new;
end

plot(x, u);

Pattern 3: Batch Processing

% Process multiple files
files = dir('data/*.csv');
results = cell(length(files), 1);

for i = 1:length(files)
    data = readtable(fullfile(files(i).folder, files(i).name));
    results{i} = analyze(data);  % Custom analysis function
end

% Combine results
all_results = vertcat(results{:});

Reference Files

• matrices-arrays.md - Matrix creation, indexing, manipulation, and operations
• mathematics.md - Linear algebra, calculus, ODEs, optimization, statistics
• graphics-visualization.md - 2D/3D plotting, customization, export
• data-import-export.md - File I/O, tables, data formats
• programming.md - Functions, scripts, control flow, OOP
• python-integration.md - Calling Python from MATLAB and vice versa
• octave-compatibility.md - Differences between MATLAB and GNU Octave
• executing-scripts.md - Executing generated scripts and for testing

GNU Octave Compatibility

GNU Octave is highly compatible with MATLAB. Most scripts work without modification. Key differences:

• Use # or % for comments (MATLAB only %)
• Octave allows ++, --, += operators
• Some toolbox functions unavailable in Octave
• Use pkg load for Octave packages

For complete compatibility guide, see references/octave-compatibility.md.

Best Practices

1. Vectorize operations - Avoid loops when possible:

   % Slow
   for i = 1:1000
       y(i) = sin(x(i));
   end
   
   % Fast
   y = sin(x);
   

2. Preallocate arrays - Avoid growing arrays in loops:

   % Slow
   for i = 1:1000
       y(i) = i^2;
   end
   
   % Fast
   y = zeros(1, 1000);
   for i = 1:1000
       y(i) = i^2;
   end
   

3. Use appropriate data types - Tables for mixed data, matrices for numeric:

   % Numeric data
   M = readmatrix('numbers.csv');
   
   % Mixed data with headers
   T = readtable('mixed.csv');
   

4. Comment and document - Use function help:

   function y = myfunction(x)
   %MYFUNCTION Brief description
   %   Y = MYFUNCTION(X) detailed description
   %
   %   Example:
   %       y = myfunction(5);
       y = x.^2;
   end
   

Additional Resources

• MATLAB Documentation: https://www.mathworks.com/help/matlab/
• GNU Octave Manual: https://docs.octave.org/latest/
• MATLAB Onramp (free course): https://www.mathworks.com/learn/tutorials/matlab-onramp.html
• File Exchange: https://www.mathworks.com/matlabcentral/fileexchange/