y = filter(b,a,x)[y,zf] = filter(b,a,x)y = filter(b,a,x,zi)
filter filters a data sequence using a digital filter. The filter realization is the transposed direct form II structure, which can handle both FIR and IIR filters [1].
y = filter(b,a,x) filters the data in vector x with the filter described by numerator coefficient vector b and denominator coefficient vector a to create the filtered data vector y. If a(1) ~= 1, filter normalizes the filter coefficients by a(1). If a(1) = 0, filter returns an error.
[y,zf] = filter(b,a,x) returns the final state values in vector zf.
y = filter(b,a,x,zi) specifies initial state conditions in vector zi.
The size of the initial/final condition vector is max(size(a),size(b)).
filter works for both real and complex inputs.
filter is implemented as a transposed direct form II structure,
where n-1 is the filter order.
The operation of filter at sample m is given by the time domain difference equations
The input-output description of this filtering operation in the z-transform domain is a rational transfer function,
filter2filticin the Signal Processing Toolbox
(c) Copyright 1994 by The MathWorks, Inc.