tfr_a.m

linear time－frequency toolbox

function [c,Ls]=tfr_a(self,f,L,dim)
%TFR_A  Analysis transform
%   Usage:  c=tfr_a(tfr,f)
%           c=tfr_a(tfr,f,L)
%           [c,Ls]=tfr_a(tfr,f);
%           [c,Ls]=tfr_a(tfr,f,L);
%           [c,Ls]=tfr_a(tfr,f,[],dim);
%           [c,Ls]=tfr_a(tfr,f,L,dim);
%
%   Input parameters:
%         tfr   : Time/frequency representation handle.
%         f     : Input data
%         L     : Length of transform to do.
%         dim   : Dimension of which to do the transform.
%   Output parameters:
%         c     : Array of coefficients.
%         Ls    : Length of input signal.
%
%   TFR_A(tfr,f) computes the analysis transform of the signal f as
%   specified by tfr.
%
%   The length of the transform will be the smallest possible that is
%   larger than the signal. f will be zero-extended to the length of the 
%   transform. If f is a matrix, the transformation is applied to each column.
%
%   The length of the transform done can be obtained by L=size(c,2)*a;   
%
%   TFR_A(tfr,f,L) computes the analysis transform as above, but does
%   a transform of length L. f will be cut or zero-extended to length L
%   before the transform is done.
%
%   [c,Ls]=TFR_A(tfr,f) or [c,Ls]=TFR_A(tfr,f,L) additionally returns the
%   length of the input signal f. This is handy for reconstruction:
% 
%                [c,Ls]=tfr_a(tfr,f)
%                fr=tfr_s(c,Ls);
% 
%   will reconstruct the signal f no matter what the length of f is, provided
%   that the analysis and synthesis window of tfr are dual windows.
%
%   TFR_A(tfr,f,[],dim) applies the transformation along dimension dim.
%   TFR_A(tfr,f,L,dim) does the same, but pads or truncates to length L.
%
%   SEE ALSO:  TFR_CREATE, TFR_S, TFR_AR, TFR_CLEAR


error(nargchk(2,4,nargin));

D=ndims(f);

if nargin<4
  dim=1;
else
  if (prod(size(dim))~=1 || ~isnumeric(dim))
    error('dim must be a scalar.');
  end;
  if rem(dim,1)~=0
    error('dim must be an integer.');
  end;
  if (dim<1) || (dim>D)
    error(sprintf('dim must be in the range from 1 to %d.',D));
  end;
end;

if nargin<3
  L=-1;
else
  if isempty(L)
    L=-1;
  end;    
end;

if dim>1
  D=ndims(f);
  order=[dim, 1:dim-1,dim+1:D];

  % Put the desired dimension first.
  f=permute(f,order);

end;

% Remember the exact size for later.
permutedsize=size(f);
  
% Reshape f to a matrix.
f=reshape(f,size(f,1),prod(size(f))/size(f,1));

% Let comp_a do all the work.
[c,Ls]=comp_a(self,f,0,'TFR_A',L);

% Remember that we changed the length of the first dim.
permutedsize(1)=size(c,1);

% Restore the original, permuted shape, except for the first dimension
% which changed.
c=reshape(c,permutedsize);

if dim>1
  % Undo the permutation.
  c=ipermute(c,order);
end;