Nonuniform fast Fourier transform
Xis a vector, then
nufftreturns the transform of the vector.
Xis a matrix, then
nuffttreats the columns of
Xas vectors and returns the transform of each column.
Xis a multidimensional array, then
nuffttreats the values along the first array dimension whose size does not equal 1 as vectors and returns the transform of each vector.
discrete Fourier transform of
Y = nufft(
X, and is equivalent to
Nonuniform Sample Points
Create a signal
X sampled at unevenly spaced points
t. Compute the nonuniform fast Fourier transform
t = [0:300 500.5:700.5]; S = 2*sin(0.1*pi*t) + sin(0.02*pi*t); X = S + rand(size(t)); Y = nufft(X,t);
Plot the absolute value of the transform as a function of the default frequencies.
n = length(t); f = (0:n-1)/n; plot(f,abs(Y))
Frequencies of Musical Chord
Define and label the frequencies of a range of musical tones.
C3 = 440 / (2^(21/12)); nOctaves = 3; musicalTones = C3 * 2.^((0:(12*nOctaves-1))/12); toneNames = ["C";"C#";"D";"D#";"E";"F";"F#";"G";"G#";"A";"A#";"B"] + string(3:(3+nOctaves-1)); toneNames = categorical(toneNames, toneNames);
Define the audio signal sampling frequency in Hz, the sample points
n, and a signal containing a major chord
fs = 16e3; n = 1:16000; X = 4*cos(2*pi*(440/fs)*n) + 2*cos(2*pi*(554.37/fs)*n) + 3*cos(2*pi*(659.2/fs)*n);
Compute and plot the frequency components of the major chord.
Y = nufft(X,,musicalTones/fs); bar(toneNames(:),abs(Y))
X — Input array
vector | matrix | multidimensional array
Input array, specified as a vector, matrix, or multidimensional array.
Complex Number Support: Yes
t — Sample points
0:(n-1) (default) | vector
Sample points, specified as a vector of length n, where
n is the length of the operating dimension of the input array
X. By default, the sample points vector is
f — Query points
0:(n-1)/n (default) | vector
Query points, specified as a vector. By default, the query points vector is
(0:(n-1))/n, where n is the length of the
operating dimension of the input array
X. To specify
f without specifying sample points, use
dim — Dimension to operate along
positive integer scalar
Dimension to operate along, specified as a positive integer scalar. The default is the first array dimension whose size does not equal 1.
Nonuniform Discrete Fourier Transform of Vector
For a vector X of length n, sample points t, and frequencies f, the nonuniform discrete Fourier transform of X is defined as
where k = 1, 2, …, m. When
t = 0, 1, …, n-1 and f = (0, 1,
…, n-1)/n (defaults for
formula is equivalent to the uniform discrete Fourier transform used by the
 Potter, Samuel F., Nail A. Gumerov, and Ramani Duraiswami. “Fast Interpolation of Bandlimited Functions.” In 2017 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 4516–20. New Orleans, LA: IEEE, 2017. https://doi.org/10.1109/ICASSP.2017.7953011.
 Dutt, A., and V. Rokhlin. “Fast Fourier Transforms for Nonequispaced Data.” SIAM Journal on Scientific Computing 14, no. 6 (November 1993): 1368–93. https://doi.org/10.1137/0914081.
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This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.