yline — Draw horizontal reference lines on current or specified axes with MATLAB-compatible styling forms.

yline adds one or more horizontal reference lines with optional labels, line specs, and name-value styling, following MATLAB-compatible plotting behavior.

Syntax

h = yline(y)
h = yline(y, styleOrLabel)
h = yline(y, LineSpec, label)
h = yline(y, Name, Value, ...)

Inputs

Returns

Errors

How yline works

• yline(y) adds a horizontal reference line at each coordinate in y. Coordinates may use any native integer class and cross to the graphics coordinate domain after validation.
• Reference lines append to the current axes without replacing existing plot content.
• Line spans follow the active axes limits, including later xlim and ylim changes.
• The returned handle supports get and set for Value, Color, LineWidth, LineStyle, Label, LabelOrientation, DisplayName, and Visible.
• Integer RGB components must be zero or one, integer line widths must be positive, and numeric Visible values must be exactly zero or one.

Examples

Add a zero baseline

plot(-5:5, (-5:5).^2 - 10);
yline(0, 'k', 'LineWidth', 1);

Expected output:

% Adds a black horizontal reference line at y = 0

Label a baseline

plot(1:10, rand(1, 10));
yline(0.5, ':', 'Baseline', 'LabelOrientation', 'horizontal');

Expected output:

% Adds a dotted labeled horizontal reference line

Rendered yline example

time = 0:0.2:10;
current = 7.2 + 0.35*time + 0.9*sin(1.3*time);
limit = 11;

plot(time, current, 'LineWidth', 2);
yline(limit, '--r', 'Operating limit', 'LineWidth', 1.5);
title('Motor Current During Ramp');
xlabel('Time (s)');
ylabel('Current (A)');
grid on;

Compare this result with other chart types in the MATLAB Plot Gallery.

Using yline with coding agents

Open a RunMat example with live inputs, then ask the agent to explain how yline changes the result.

Related Plotting functions

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