interp1 — Interpolate one-dimensional sampled data at query points.

interp1(x, y, xq) estimates values of a one-dimensional data set at query points xq. The default method is linear interpolation; nearest, spline, and pchip are also accepted.

Syntax

yq = interp1(y, xq)
yq = interp1(x, y, xq)
yq = interp1(x, y, xq, method)
yq = interp1(x, y, xq, method, 'extrap')

• x is a strictly increasing vector of sample locations. When omitted, RunMat uses 1:numel(y).
• y contains the sampled values. Vector inputs produce vector outputs; matrix inputs are interpolated along the sample dimension.
• xq contains query points. Scalar queries return scalars, and array queries preserve their shape.
• method may be linear, nearest, spline, or pchip. The default is linear.
• Out-of-range queries return NaN by default. Pass 'extrap' to extrapolate or pass a scalar fill value.

How interp1 works

• interp1(y, xq) uses implicit sample points 1:numel(y).
• interp1(x, y, xq, method) supports linear, nearest, spline, and pchip.
• Out-of-range query points return NaN unless an extrapolation value or 'extrap' is supplied.
• Dense real numeric arrays are supported. GPU inputs gather to the host reference path.

Examples

Linear interpolation

x = [1 2 3];
y = [10 20 40];
yq = interp1(x, y, [1.5 2.5])

Expected output:

yq = [15 30]

Spline interpolation

x = [1 2 3];
y = [1 4 9];
yq = interp1(x, y, [1.5 2.5], 'spline')

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 interp1 works, line by line, in Rust.

• View interp1.rs on GitHub
• Learn how the runtime works
• Found a bug? Open an issue with a minimal reproduction.

About RunMat

RunMat is an open-source runtime that executes MATLAB-syntax code — faster, on any GPU, with no license required.

• Simulations that took hours now take minutes. RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed.
• Start running code in seconds. Open the browser sandbox or download a single binary. No license server, no IT ticket, no setup.
• A full development environment. GPU-accelerated 2D and 3D plotting, automatic versioning on every save, and a browser IDE you can share with a link.

Getting started · Benchmarks · Pricing