I hope that someday Octave will include more signal processing functions. If you would like to help improve Octave in this area, please contact bug-octave@bevo.che.wisc.edu.
detrend (x, p)
removes the
best fit of a polynomial of order p from the data x.
If x is a matrix, detrend (x, p)
does the same
for each column in x.
The second argument is optional. If it is not specified, a value of 1
is assumed. This corresponds to removing a linear trend.
fft
computes the FFT for each column of a.
If called with two arguments, n is expected to be an integer specifying the number of elements of a to use. If a is a matrix, n specifies the number of rows of a to use. If n is larger than the size of a, a is resized and padded with zeros.
fft
computes the inverse FFT for each column
of a.
If called with two arguments, n is expected to be an integer specifying the number of elements of a to use. If a is a matrix, n specifies the number of rows of a to use. If n is larger than the size of a, a is resized and padded with zeros.
The optional arguments n and m may be used specify the number of rows and columns of a to use. If either of these is larger than the size of a, a is resized and padded with zeros.
The optional arguments n and m may be used specify the number of rows and columns of a to use. If either of these is larger than the size of a, a is resized and padded with zeros.
length (a) + length (b) - 1
. If a
and b are the coefficient vectors of two polynomials, the returned
value is the coefficient vector of the product polynomial.
The computation uses the FFT by calling the function fftfilt
. If
the optional argument n is specified, an N-point FFT is used.
fftfilt
filters x with the FIR filter
b using the FFT.
Given the optional third argument, n, fftfilt
uses the
overlap-add method to filter x with b using an N-point FFT.
N M SUM a(k+1) y(n-k) = SUM b(k+1) x(n-k) for 1<=n<=length(x) k=0 k=0
where N=length(a)-1 and M=length(b)-1. An equivalent form of this equation is:
N M y(n) = - SUM c(k+1) y(n-k) + SUM d(k+1) x(n-k) for 1<=n<=length(x) k=1 k=0
where c = a/a(1) and d = b/a(1).
If the fourth argument si is provided, it is taken as the initial state of the system and the final state is returned as sf. The state vector is a column vector whose length is equal to the length of the longest coefficient vector minus one. If si is not supplied, the initial state vector is set to all zeros.
In terms of the z-transform, y is the result of passing the discrete- time signal x through a system characterized by the following rational system function:
M SUM d(k+1) z^(-k) k=0 H(z) = ---------------------- N 1 + SUM c(k+1) z(-k) k=1
% DO NOT EDIT! Generated automatically by munge-texi.
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