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
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
y | NumericArray | Yes | — | Y-coordinate scalar or numeric vector of horizontal line positions. |
style_or_label | Any | No | — | LineSpec token (for example '--r') or label text. |
linespec | StyleSpec | Yes | — | Line style token (for example '--r'). |
label | StringScalar | Yes | — | Reference line label text. |
props | Any | Variadic | — | Style arguments and Name/Value pairs (Color, LineWidth, LineStyle, LabelOrientation, Visible). |
Returns
| Name | Type | Description |
|---|---|---|
h | NumericArray | Reference line handle scalar or row vector when multiple coordinates are provided. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:yline:InvalidArgument | Coordinate input, style arguments, or Name/Value pairs are invalid. | yline: invalid argument |
RunMat:yline:Internal | Internal plotting state update fails. | yline: internal operation failed |
How yline works
yline(y)adds a horizontal reference line at each coordinate iny.- Reference lines append to the current axes without replacing existing plot content.
- Line spans follow the active axes limits, including later
xlimandylimchanges. - The returned handle supports
getandsetforValue,Color,LineWidth,LineStyle,Label,LabelOrientation,DisplayName, andVisible.
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 = 0Label a baseline
plot(1:10, rand(1, 10));
yline(0.5, ':', 'Baseline', 'LabelOrientation', 'horizontal');Expected output:
% Adds a dotted labeled horizontal reference lineUsing yline with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how yline changes the result.
Run a small yline example, explain the result, then change one input and compare the output.
Related Plotting functions
About RunMat
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