fftn — Compute an N-dimensional discrete Fourier transform.
fftn(X) transforms every dimension of X. fftn(X,SIZE) pads or truncates each transformed dimension according to a positive integer size vector whose length is at least ndims(X).
Syntax
Y = fftn(X)
Y = fftn(X, SIZE)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
X | Any | Yes | — | Input array. |
SIZE | NumericArray | No | — | Positive transform-size vector with length at least ndims(X). |
Returns
| Name | Type | Description |
|---|---|---|
Y | NumericArray | N-D complex Fourier spectrum output. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:fftn:ArgCount | More than two input arguments are supplied. | fftn: invalid argument count |
RunMat:fftn:InvalidSize | SIZE argument is invalid. | fftn: invalid SIZE argument |
RunMat:fftn:InvalidInput | Input cannot be converted to supported numeric/complex domain. | fftn: invalid input |
RunMat:fftn:Internal | FFTN execution or tensor shaping fails. | fftn: internal error |
How fftn works
- Integer inputs through 32 bits and logical inputs are documented and produce double output; single input produces single output.
SIZEmust be a row or column vector of positive integers with at least one entry per input dimension.- RunMat extension mode can admit exact int64 and uint64 structural controls and positive SIZE vectors shorter than
ndims(X)through independent gates. - gpuArray results remain resident when a provider hook succeeds or when RunMat completes a supported fallback on the host.
Examples
Transforming every dimension of a volume
X = rand(4, 5, 6);
Y = fftn(X)Padding an N-dimensional transform
X = rand(4, 5, 6);
Y = fftn(X, [8 8 8])Using fftn with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how fftn changes the result.
Run a small fftn example, explain the result, then change one input and compare the output.
FAQ
What shape does fftn(X,SIZE) return?⌄
Its transformed dimensions have the lengths listed in SIZE; the compatibility form requires length(SIZE) >= ndims(X).
What precision is used for integer input?⌄
Documented integer classes enter the double-precision FFT domain and return double 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 fftn is executed, line by line, in Rust.
- View the source for fftn 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.
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