function P = polyphase(varargin)

% POLYPHASE -- convert matrix polynomial to polyphase form
% 
%         P = polyphase(P,m,r)
%         P = polyphase(P)
% 
% If P has type '', both M and R must be given. This routine will
% attach M, R to P and rearrange the coefficients into polyphase form.
%
% If P has type 'polyphase', the same P is returned.
%
% If P has type 'symbol', P is scaled by sqrt(m), and the coefficients
% are rearranged into polyphase form.

% Copyright (c) 2004 by Fritz Keinert (keinert@iastate.edu),
% Dept. of Mathematics, Iowa State University, Ames, IA 50011.
% This software may be freely used and distributed for non-commercial
% purposes, provided this copyright statement is preserved, and
% appropriate credit for its use is given.
%
% Last update: Feb 20, 2004

switch varargin{1}.type
 case ''
% P = polyphase(P,m,r)
  if (nargin < 3)
      error('M and R must be given');
  end
  P = varargin{1};
  m = varargin{2};
  r = varargin{3};
  [n1,n2] = size(P);
  if (n2 ~= r | round(n1/r)*r ~= n1)
      error('size of P is not compatible with given R');
  end
  newmin = P.min - mod(P.min,m);
  Pmax = get(P,'max');
  newmax = Pmax + (m-1-mod(Pmax,m))
  P = trim(P,[newmin,newmax]);
  P = reshape(P,n1,m*r);
  P.type = 'polyphase';
  P.m = m;
  P.r = r;
 
 case 'polyphase'
% P = polyphase(P)
  P = varargin{1};
 
 case 'symbol'
% P = polyphase(P)
  P = varargin{1};
  m = P.m;
  r = P.r;
  [n1,n2] = size(P);
  newmin = P.min - mod(P.min,m);
  Pmax = get(P,'max');
  newmax = Pmax + (m-1-mod(Pmax,m));
  P = trim(P,[newmin,newmax]);
  P = reshape(P,n1,m*r);
  P.type = 'polyphase';
  P.min = P.min / m;
  P = P * sqrt(m);
  
 otherwise
  disp('this should not happen');
  keyboard
end