MATLAB Programming

5 Types of Functions
% FILTFCN. Each time you call FILTFCN with a new filter
% input value, it computes the corresponding new filter
% output value, updating its internal state vector at the
% same time.
%
% [FILTFCN, STATEFCN] = MAKEFILTER(B, A) also returns a
% function (in the form of a function handle, STATEFCN)
% that can return the filter's internal state. The internal
% state vector is in the form of a transposed direct form
% II delay line.
% Initialize state vector. To keep this example a bit
% simpler, assume that a and b have the same length.
% Also assume that a(1) is 1.
v = zeros(size(a));
filtfcn = @iirFilter;
statefcn = @getState;
function yn = iirFilter(xn)
% Update the state vector
v(1) = v(2) + b(1) * xn;
v(2:end-1) = v(3:end) + b(2:end-1) * xn - a(2:end-1) * v(1);
v(end) = b(end) * xn - a(end) * v(1);
% Output is the first element of the state vector.
yn = v(1);
end
function vOut = getState
vOut = v;
end
end
This sample session shows how makeFilter works. Make a filter that has
a decaying exponential impulse response and then call it a few times in
succession to see the output values change:
[filt1, state1] = makeFilter([1 0], [1 -.5]);
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