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
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
X | Any | Yes | — | Strictly increasing sample locations. |
Y | Any | Yes | — | Sample values. |
Xq | Any | Yes | — | Query points. |
Returns
| Name | Type | Description |
|---|---|---|
pp | Any | Piecewise-polynomial struct representation. |
Vq | NumericArray | Spline-evaluated values at query points. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:spline:InvalidArgument | Argument count or interpolation option grammar is invalid. | spline: invalid argument |
RunMat:spline:InvalidInput | Sample/query inputs are invalid for spline construction or evaluation. | spline: invalid input |
RunMat:spline:Internal | Spline coefficient generation or tensor assembly fails internally. | spline: internal interpolation failure |
How spline works
- Returns a pp structure with
form,breaks,coefs,pieces,order, anddimfields. - The direct evaluation form extrapolates outside the sample range, matching MATLAB's standalone
splinebehavior. - Dense real numeric inputs are supported in the initial implementation.
- The documented storage classes for sample locations, sample values, and query points are single and double. Typed integer values in any of those roles are separate RunMat-only extensions and reject before interpolation if conversion to binary64 would round.
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 = 2.25Using spline with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how spline changes the result.
Run a small spline 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 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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