MATLAB - Commands

MATLAB - Modern Command-Line Usage

MATLAB provides a powerful interactive environment for numerical computation, data analysis, and visualization. You can execute commands directly in the Command Window at the >> prompt. This tutorial covers essential commands for a modern MATLAB workflow.

We will explore commands for managing your session, interacting with the file system, handling I/O, and working with MATLAB’s core data structures.

Workspace and Session Management

These commands help you manage the variables in your workspace and control your MATLAB session. The Workspace browser in the MATLAB Desktop provides a graphical interface for these operations.

Command	Purpose
clc	Clears the Command Window text, keeping the workspace intact.
clear	Removes all variables from the current workspace. Use clear varName to remove a specific variable.
exist	Checks for the existence of a variable, file, or folder. E.g., exist('myVar', 'var').
global	Declares variables to be global, accessible across different functions. Best Practice: Use with caution; passing variables as function arguments is generally preferred.
help	Displays help text for a function in the Command Window. E.g., help plot.
doc	Opens the full documentation page for a function, which is often more detailed than help. E.g., doc plot.
lookfor	Searches the first line of help text for a keyword. Useful when you don’t know the exact function name.
quit	Stops MATLAB.
who	Lists the names of variables in the current workspace.
whos	Lists current variables with details like size, bytes, and class.

File System and Data I/O

Modern data science requires robust tools for importing and exporting data. MATLAB excels at handling various file formats, from simple text files to large datasets.

Command	Purpose
cd	Changes the current directory. Use cd .. to go up one level.
dir	Lists the contents of the current directory.
pwd	Displays the current working directory path.
load / save	Loads and saves workspace variables to a MATLAB-specific .mat file. E.g., save('mySession.mat').
readtable	Modern Best Practice. Reads tabular data from files like .csv or .xlsx into a table data type.
writetable	Modern Best Practice. Writes a table to a file like .csv or .xlsx.
readmatrix / writematrix	Reads/writes purely numeric data from/to text or spreadsheet files.
delete	Deletes a file. Use with caution.
type	Displays the contents of a text-based file (e.g., a .m script).
diary	Creates a log of commands and output from your MATLAB session.
wklread	Deprecated. This function was used for older Lotus 1-2-3 spreadsheets. Use readtable or readmatrix for modern spreadsheet files.

Command Window Input and Output

These commands control how information is displayed in the Command Window and how user input is received.

Command	Purpose
disp	Displays the contents of an array or string without printing the variable name. Useful for showing messages.
fprintf	Writes formatted data to the screen or a file, offering fine-grained control over the output. Similar to C’s printf.
input	Displays a prompt and waits for the user to enter a value.
format	Controls the numeric display format in the Command Window (e.g., format long, format short, format bank).
; (semicolon)	Suppresses the output of a command. Essential for preventing large matrices from flooding the screen.

Array, Matrix, and Table Commands

MATLAB’s core strength is its handling of arrays and matrices. The following commands are fundamental for data manipulation.

Command	Purpose
size	Returns the dimensions of an array.
length	Returns the length of the largest array dimension. For a vector, it’s the number of elements.
numel	Returns the total number of elements in an array.
reshape	Changes the size and shape of an array while preserving the number of elements.
zeros, ones, eye	Creates arrays of all zeros, all ones, or an identity matrix, respectively.
linspace, logspace	Creates linearly or logarithmically spaced vectors.
max, min, sum, prod	Computes the maximum, minimum, sum, or product of array elements.
sort	Sorts array elements in ascending order.
find	Finds indices and values of nonzero elements, or elements that satisfy a logical condition.
det, inv, rank	Computes the determinant, inverse, and rank of a matrix.
cross, dot	Computes vector cross products and dot products.
table	Modern Data Structure. Creates a table, which can hold columns of different data types (numeric, text, categorical).
cell	Creates a cell array, which can hold different types and sizes of data in each element.

Modern Plotting Commands

MATLAB offers a powerful and flexible graphics system. The modern approach involves creating plot objects and modifying their properties for full control over visualization.

Command	Purpose
plot	Creates a 2D line plot. Returns a plot object for further customization. E.g., p = plot(x, y); p.LineWidth = 2;.
scatter	Creates a 2D scatter plot with markers.
bar	Creates a bar chart.
histogram	Creates a histogram to visualize data distribution.
heatmap	Creates a heatmap from a matrix.
xlabel, ylabel, title, legend	Adds labels, a title, and a legend to the current axes.
figure	Creates a new figure window.
tiledlayout	Modern Best Practice. Creates and arranges a grid of plots within a figure. Preferred over subplot.
subplot	Creates subplots in a grid. tiledlayout is recommended for newer code.
hold on / hold off	Allows multiple plots to be drawn on the same axes without overwriting.
axis	Sets or gets the axis limits. E.g., axis([xmin xmax ymin ymax]).
grid on / grid off	Toggles the visibility of grid lines.
exportgraphics	Modern Best Practice. Saves a figure or axes to a file (e.g., PNG, PDF, EPS). Preferred over print.