interp1 — Interpolate one-dimensional sampled data in MATLAB and RunMat.
interp1(x, y, xq) estimates values of one-dimensional sampled data at query points xq. Default interpolation is linear, with additional methods such as nearest, spline, and pchip following MATLAB semantics.
Syntax
Vq = interp1(Y, Xq)
Vq = interp1(X, Y, Xq)
Vq = interp1(Y, Xq, method)
Vq = interp1(X, Y, Xq, method)
Vq = interp1(Y, Xq, extrap)
Vq = interp1(X, Y, Xq, extrap)
Vq = interp1(Y, Xq, method, extrap)
Vq = interp1(X, Y, Xq, method, extrap)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
Y | Any | Yes | — | Sample values at implicit X = 1:numel(Y). |
Xq | Any | Yes | — | Query points. |
X | Any | Yes | — | Sample locations. |
Y | Any | Yes | — | Sample values. |
method | StringScalar | No | "linear" | Interpolation method: "linear", "nearest", "spline", or "pchip". |
extrap | Any | No | NaN | Extrapolation mode: "extrap" or scalar fill value. |
Returns
| Name | Type | Description |
|---|---|---|
Vq | NumericArray | Interpolated values at query points. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:interp1:InvalidArgument | Argument count, method/extrapolation options, or shape constraints are invalid. | interp1: invalid argument |
RunMat:interp1:InvalidInput | Sample or query values cannot be converted to numeric interpolation domains. | interp1: invalid input |
RunMat:interp1:Internal | Interpolation evaluation fails due to internal tensor construction or solver paths. | interp1: internal interpolation failure |
How interp1 works
interp1(y, xq)uses implicit sample points1:numel(y).interp1(x, y, xq, method)supportslinear,nearest,spline, andpchip.- Out-of-range query points return
NaNunless an extrapolation value or'extrap'is supplied. - Dense real numeric arrays are supported. Real gpuArray Y/query inputs stay resident for linear and nearest interpolation when X is implicit or host-validated.
GPU memory and residency
interp1 uploads implicit or host-validated sample points, evaluates linear/nearest queries with provider interp1, and returns a resident gpuArray output. Spline, pchip, complex, and resident-X validation paths use the host implementation until dedicated validation/interpolation kernels cover those cases.
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]Resident GPU linear interpolation
Y = gpuArray([10 20 40]);
Vq = interp1(Y, gpuArray([1.5 2.5]))Expected output:
Vq = gpuArray([15 30])Using interp1 with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how interp1 changes the result.
Run a small interp1 example, explain the result, then change one input and compare the output.
Related Math functions
Elementwise
abs · angle · bsxfun · complex · conj · double · erf · erfcinv · exp · expm1 · factorial · flintmax · gamma · gammaln · heaviside · hypot · idivide · imag · intmax · intmin · ldivide · log · log10 · log1p · log2 · minus · nextpow2 · plus · pow2 · power · rdivide · real · realmax · realmin · realsqrt · rescale · sign · single · sqrt · swapbytes · times · typecast · uint16 · uint32 · uint8
Trigonometry
acos · acosh · asin · asinh · atan · atan2 · atanh · cos · cosd · cosh · cospi · deg2rad · pol2cart · rad2deg · sin · sind · sinh · sinpi · tan · tand · tanh
Reduction
all · any · bounds · cummax · cummin · cumprod · cumsum · cumtrapz · diff · gradient · max · maxk · mean · median · min · mink · movmax · movmean · movmedian · movmin · movprod · movstd · movsum · movvar · nnz · prod · rms · std · sum · trapz · var
Structure
bandwidth · isdiag · ishermitian · issymmetric · istril · istriu · symrcm
Signal
blackman · butter · buttord · cheb2ord · conv · conv2 · deconv · downsample · envelope · filter · filtfilt · fir1 · freqz · gauspuls · hamming · hann · hilbert · periodogram · pulstran · pwelch · rectpuls · resample · sawtooth · sinc · spectrogram · square · tripuls · unwrap · upsample · zplane
Optim
coneprog · fminbnd · fminunc · fsolve · fzero · integral · linprog · lsqcurvefit · lsqnonlin · optimoptions · optimset · quad · secondordercone
Ops
cross · ctranspose · dot · mldivide · mpower · mrdivide · mtimes · pagemtimes · pagetranspose · trace · transpose
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how interp1 is executed, line by line, in Rust.
- View the source for interp1 in Rust on GitHub
- Learn how the RunMat 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 blazing on any GPU. It is licensed under the Apache 2.0 license.
- RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
- Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.