shrink

 SHRINK - Removes outer zeros of a matrix.

   Y = SHRINK(X) removes the outer columns/rows/etc (borders) that
   contains only zeros on a matrix X. The shrinking goes on untill
   the first column/row/etc containing a nonzero element is found

   Examples: SHRINK([0 0 1 0 2 3 0]) = [1 0 2 3]

             SHRINK([[0 0 0 0 0 0 0]  = [[0 0 1 2]
                      0 0 0 1 2 0 0]     [0 0 0 0]
                      0 0 0 0 0 0 0]     [3 0 0 0]]
                      0 3 0 0 0 0 0]])

  Y = SHRINK(X,E) removes columns/rows/etc containing only the 
  element E, intead of zero.

  [Y,Li,Ls] = SHRINK(...) also returns the limits of the shrinking,
  Li = inferior limits and Ls = superior limits.

    See also GROW, ROLL, PAD, PADC.

0001 function [Y, varargout] = shrink(X,E)
0002 
0003 % SHRINK - Removes outer zeros of a matrix.
0004 %
0005 %   Y = SHRINK(X) removes the outer columns/rows/etc (borders) that
0006 %   contains only zeros on a matrix X. The shrinking goes on untill
0007 %   the first column/row/etc containing a nonzero element is found
0008 %
0009 %   Examples: SHRINK([0 0 1 0 2 3 0]) = [1 0 2 3]
0010 %
0011 %             SHRINK([[0 0 0 0 0 0 0]  = [[0 0 1 2]
0012 %                      0 0 0 1 2 0 0]     [0 0 0 0]
0013 %                      0 0 0 0 0 0 0]     [3 0 0 0]]
0014 %                      0 3 0 0 0 0 0]])
0015 %
0016 %  Y = SHRINK(X,E) removes columns/rows/etc containing only the
0017 %  element E, intead of zero.
0018 %
0019 %  [Y,Li,Ls] = SHRINK(...) also returns the limits of the shrinking,
0020 %  Li = inferior limits and Ls = superior limits.
0021 %
0022 %    See also GROW, ROLL, PAD, PADC.
0023 %
0024 
0025 if nargin==1
0026    E = 0;
0027 end
0028 
0029 % If X is row vector transform to col vector (to prevent problems with find)
0030 flagrow = 0;
0031 if ndims(X)==2 & size(X,1)==1 & size(X,2)>=1
0032    X = X';
0033    flagrow = 1;
0034 end
0035 
0036 % Finding columns/rows/etc to be extracted
0037 c = ind2subm( size(X), find(X~=E) );
0038 
0039 % Get minimuns and maximuns founds
0040 li = min(c,[],1)';
0041 ls = max(c,[],1)';
0042 
0043 % Mounting text: li(1):ls(1),li(2):ls(2)...
0044 N = ndims(X);
0045 for i = 1 : N
0046    ind{i} = li(i):ls(i);
0047 end
0048 
0049 % Making Y
0050 Y = X(ind{:});
0051 
0052 % De-transposing is X is row vector
0053 if flagrow
0054    Y = Y';
0055 end
0056 if nargout>1
0057    varargout{1} = li';
0058    varargout{2} = ls';
0059 end