iir2fir.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function g=iir2fir(g,L,symmetri);
%IIR2FIR   Cut IIR window to FIR
%   Usage:  g=iir2fir(g,L);
%
%   IIR2FIR(g,L) will cut the IIR window g to a length L FIR window by
%   cutting out the middle part. Note that this is a slightly different
%   behaviour than MIDDLEPAD.
%
%   IIR2FIR(g,L,'wpe') or IIR2FIR(g,L,'hpe') does the same assuming the input
%   window is a WPE or HPE window, respectively.
%
%   SEE ALSO:  FIREXTEND, MIDDLEPAD

% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

error(nargchk(2,3,nargin));

W=length(g);

if W<L
  error('L must be smaller than length of window.');
end;


if nargin==2
  % No assumption on the symmetri of the window.

  if rem(L,2)==0
    % HPE middlepad works the same way as the FIR cutting (e.g. just
    % removing middle points) for even values of L.
    g=middlepad(g,L,[],.5);
  else
    % WPE middlepad works the same way as the FIR cutting (e.g. just
    % removing middle points) for odd values of L.
    g=middlepad(g,L);
  end;
  
else
  switch(lower(symmetri))
    case 'wpe'
      g=middlepad(g,L);
      if rem(L,2)==0
	g(L/2+1)=0;
      end;
    case 'hpe'
      g=middlepad(g,L,[],.5);
      if rem(L,2)==1
	g(ceil(L/2))=0;
      end;
    otherwise
      error('Unknown symmetri.');
  end;
end;