reindex(x,y)

function xout = reindex(x,y)
%REINDEX(x,y) add dimensions to make x look like y
%   Assume they share some dimensions in common (as many as you like)
%   Requirements: size(y) must contain all non-singleton elements in size(x)
%                 y cannot have two dimension of the same length
%   examples:
%   x = [1 2 3 4 5]; z = ones([23 5 1 6]); g = reindex(x,z);
%   x = [1 2 3 4 5; 6 7 8 9 10]; z = ones([23 5 6 2 4]); g = reindex(x,z);
%   g will have size of z
%
%   Will Fox, 2005
%   modified by Noam Katz, 7/7/06

sy0 = size(y);
sx0 = size(x);

if prod(sx0)~=prod(sy0)		%if need to add non-singleton dimensions (if only singleton dim needed, see reshape below)
   %remove singleton dimesnsions from x,y 
   x = sq(x);
   sy = sy0(sy0~=1);
   sx = sx0(sx0~=1);
   
   %sort dimensions by their length
   [sx,jj] = sort(sx);
   [sy,kk] = sort(sy);
   if size(x,2)==1	%if a vector, make it 1 x N
      x = x';
   elseif size(x,1)~=1
      x = permute(x,jj);
   end

   %check that problem is well-posed
   for j=1:length(sx)
   	if isempty(find(sy==sx(j), 1))
   	   error('all of x dimensions must be y dimensions also (i.e. if sx = [1 80 3], sy could be [80 3 23 2] but not [80 23 2])')
   	end
   end
   for k=1:length(sy)
      if sum(sy(k)==sy)>1
         error('some dimensions of y have the same length, so I''m not sure how to reindex here')
      end
   end
   
   %add dimensions as needed
   for j = 1:length(sy)
      sx(end+1:length(sy)) = 0;						%pad with zeros to prevent sx(j) from giving error
      if sx(j)~=sy(j)
         x = shiftdim(x,j-1);							%shift dimension so that new dimension should come at beginning
         if size(x,1)~=1								%if not a vector
            x = reshape(sq(x),[1 size(sq(x))]);		%add a dimension (if it is a vector it already has a leading singleton dim (was reshaped above))
         end
         x = repmat(x,[sy(j) 1]);					%replicate along that dimension
         lsx = length(size(x));
         x = shiftdim(x,lsx-(j-1));					%shift back
         sx = size(x);									
      end
   end
   
   x = ipermute(x,kk);   

   %reshape to look like y (basically, add singleton dimensions if necessary)
   xout = reshape(x,sy0);

else
   error('sizes of x and y are equal, use permute instead')
end