spline — Construct cubic spline interpolants or evaluate them at query points with MATLAB-compatible spline forms.

spline(x, y) constructs a cubic spline piecewise-polynomial representation, and spline(x, y, xq) evaluates the spline at query points. Behavior follows MATLAB-compatible interpolation conventions.

Syntax

pp = spline(X, Y)
Vq = spline(X, Y, Xq)

Inputs

Returns

Errors

How spline works

• Returns a pp structure with form, breaks, coefs, pieces, order, and dim fields.
• The direct evaluation form extrapolates outside the sample range, matching MATLAB's standalone spline behavior.
• Dense real numeric inputs are supported in the initial implementation.

Examples

Build and evaluate a spline

x = [1 2 3];
y = [1 4 9];
pp = spline(x, y);
yq = ppval(pp, [1.5 2.5])

Expected output:

yq = [2.25 6.25]

Direct evaluation

x = [1 2 3];
y = [1 4 9];
yq = spline(x, y, 1.5)

Expected output:

yq = 2.25

Using spline with coding agents

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

Related Math functions

Open-source implementation

Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how spline is executed, line by line, in Rust.

• View the source for spline in Rust on GitHub
• Learn how the RunMat runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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