www.gusucode.com > signal 工具箱matlab源码程序 > signal/@dfilt/@df1t/thisnstates.m

    function n = thisnstates(Hd)
%NSTATES  Number of states in discrete-time filter.
%   NSTATES(Hd) returns the number of states in the
%   discrete-time filter Hd.  The number of states depends on the filter
%   structure and the coefficients.
%
%   See also DFILT.   
  
%   Author: Thomas A. Bryan
%   Copyright 1988-2003 The MathWorks, Inc.

ncoeffs = Hd.ncoeffs;
n = sum(ncoeffs)-2;

% If ncoeffs defauls to [], don't have nstates return a negative value.
if n < 0, n = 0; end