How to Add Legend in MATLAB: Simple Guide

In MATLAB, you add a legend to a plot using the legend function by passing labels as strings for each plotted data series. For example, legend('Data1', 'Data2') adds a legend identifying each line or marker in the plot.

Syntax

The basic syntax to add a legend in MATLAB is:

• legend('label1', 'label2', ...): Adds a legend with specified labels for each plotted data series.
• legend('show'): Displays the legend if it was previously hidden.
• legend('off'): Hides the legend.

You can also customize the legend location and appearance using additional name-value pair arguments.

matlab

legend('label1', 'label2', ...)
legend('show')
legend('off')

Example

This example shows how to plot two lines and add a legend to identify them clearly.

matlab

x = 1:10;
y1 = x;
y2 = x.^2;
plot(x, y1, '-o', x, y2, '-*')
legend('Linear', 'Quadratic')

Output

A plot window opens showing two lines: one with circle markers labeled 'Linear' and one with star markers labeled 'Quadratic'. A legend box appears identifying each line accordingly.

Common Pitfalls

Common mistakes when adding legends in MATLAB include:

• Not matching the number of legend labels to the number of plotted data series, which causes errors or incorrect legends.
• Calling legend before plotting data, resulting in an empty or missing legend.
• Overlapping legend with plot data if the default location is not suitable.

Always ensure your legend labels correspond exactly to the plotted lines or markers.

matlab

plot(1:5)
legend('Only one label') % Correct

plot(1:5, 1:5, 1:5, (1:5).^2)
legend('One label') % Incorrect: fewer labels than lines

% Correct way:
plot(1:5, 1:5, 1:5, (1:5).^2)
legend('Line 1', 'Line 2', 'Line 3')

Quick Reference

Command	Description
legend('label1', 'label2', ...)	Add legend with specified labels
legend('show')	Show the legend if hidden
legend('off')	Hide the legend
legend('Location', 'best')	Place legend at best location automatically
legend('Location', 'northwest')	Place legend at top-left corner

Key Takeaways

Use legend with labels matching the number of plotted data series.

Call legend after plotting your data to ensure it appears correctly.

Customize legend location with the 'Location' option to avoid overlap.

Use legend('show') and legend('off') to toggle legend visibility.

Always check that legend labels clearly describe each plot element for clarity.