ppval — Evaluate a piecewise-polynomial structure.

ppval(pp, xq) evaluates a piecewise-polynomial structure produced by spline or pchip at query points xq.

Syntax

yq = ppval(pp, xq)

• pp is a piecewise-polynomial structure, typically returned by spline or pchip.
• xq contains query points. Scalar queries return scalars, and array queries preserve their shape.
• RunMat evaluates each interval with Horner's method using the pp coefficient table.
• Queries outside the break range are extrapolated from the first or last polynomial piece.

How ppval works

• Accepts pp structures with form, breaks, coefs, pieces, order, and dim fields.
• Uses Horner evaluation within each interval.
• Extrapolates outside the break range, matching MATLAB pp evaluation behavior.

Example

Evaluate a spline pp structure

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

Expected output:

yq = [2.25 6.25]

Related Math functions

Open-source implementation

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

• View ppval.rs on GitHub
• Learn how the runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

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