grow

 GROW    Expands a matrix.

   Y = GROW(X,[M1 M2 ... Mn]) creates a matrix 'Y' by the expansion
   of the matrix 'x' of Mi elements on directions i e -i. The size 
   of the new matrix 'Y' will be:
       size(Y) = size(x) + 2*[M]

   Example: X = [ 1 2 3; 4 5 6; 7 8 9]
   Y = GROW(X,[1 0])
   Y = [1 2 3; 1 2 3; 4 5 6; 7 8 9; 7 8 9]

   Y = GROW(X,[1 1])
   Y = [1 1 2 3 3; 1 1 2 3 3; 4 4 5 6 6; 7 7 8 9 9; 7 7 8 9 9]

   Y = GROW(X) uses as standard Mi = 1.

    If DIM(X)>1, GROW(X,N) = GROW(X,N*ones(DIM(x)))

   Y = GROW(X,[M], 'a') performs assimetric expansion. If Mi is even
   assimetric expansion is the same as simmetric expansion, execpt that
   the expansion in the assimetric mode will be half of the one in the
   simmetric mode. If Mi is odd, the matrix will be expanded ceil(Mi/2)
   elements in the -i direction and floor(Mi/2) in the i. The size of
   the expanded matrix will be:  
       size(y) = size(X) + [M]

  [M] can contain negative integers. In this case, the outer elements
  of X will be discarded.

    See also ROLL, PAD, PADC, SHRINK.

0001 function Y = grow(varargin)
0002 %
0003 % GROW    Expands a matrix.
0004 %
0005 %   Y = GROW(X,[M1 M2 ... Mn]) creates a matrix 'Y' by the expansion
0006 %   of the matrix 'x' of Mi elements on directions i e -i. The size
0007 %   of the new matrix 'Y' will be:
0008 %       size(Y) = size(x) + 2*[M]
0009 %
0010 %   Example: X = [ 1 2 3; 4 5 6; 7 8 9]
0011 %   Y = GROW(X,[1 0])
0012 %   Y = [1 2 3; 1 2 3; 4 5 6; 7 8 9; 7 8 9]
0013 %
0014 %   Y = GROW(X,[1 1])
0015 %   Y = [1 1 2 3 3; 1 1 2 3 3; 4 4 5 6 6; 7 7 8 9 9; 7 7 8 9 9]
0016 %
0017 %   Y = GROW(X) uses as standard Mi = 1.
0018 %
0019 %    If DIM(X)>1, GROW(X,N) = GROW(X,N*ones(DIM(x)))
0020 %
0021 %   Y = GROW(X,[M], 'a') performs assimetric expansion. If Mi is even
0022 %   assimetric expansion is the same as simmetric expansion, execpt that
0023 %   the expansion in the assimetric mode will be half of the one in the
0024 %   simmetric mode. If Mi is odd, the matrix will be expanded ceil(Mi/2)
0025 %   elements in the -i direction and floor(Mi/2) in the i. The size of
0026 %   the expanded matrix will be:
0027 %       size(y) = size(X) + [M]
0028 %
0029 %  [M] can contain negative integers. In this case, the outer elements
0030 %  of X will be discarded.
0031 %
0032 %    See also ROLL, PAD, PADC, SHRINK.
0033 %
0034 
0035 
0036 [X, M, assimetric] = parse_inputs(varargin{:});
0037 
0038 ind = cell(length(M),1);
0039 
0040 if assimetric == 0
0041    for i = 1 : length(M)
0042       if M(i) >= 0
0043          ind{i} = [repmat(1,[1 M(i)]) 1:size(X,i) repmat(size(X,i),[1 M(i)]) ];
0044       else
0045          ind{i} = 1+(-M(i)) : size(X,i)-(-M(i)); % using -M(i) to change sign
0046       end
0047    end
0048 else % if not assimetric
0049    for i = 1 : length(M)
0050       if M(i) >= 0
0051          ind{i} = [repmat(1,[1 ceil(M(i)/2)]) 1:size(X,i) repmat(size(X,i),[1 floor(M(i)/2)]) ];
0052       else
0053          ind{i} = 1+ceil(-M(i)/2) : size(X,i) - floor(-M(i)/2);
0054       end
0055    end
0056 end
0057    
0058 Y = X(ind{:});
0059 
0060 
0061 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0062 function [X,M,assimetric] = parse_inputs(varargin)
0063 assimetric = 0;
0064 
0065 switch nargin
0066 case 0
0067    error('Too few inputs!')
0068    return
0069    
0070 case 1
0071    X = varargin{1};
0072    M = ones(1,ndims(X));
0073    
0074 case 2
0075    X = varargin{1};
0076    M = varargin{2};
0077    if strcmp(M,'a')
0078       M = ones(1,ndims(X));
0079       assimetric = 1;
0080    end
0081    
0082 case 3
0083    X = varargin{1};
0084    M = varargin{2};
0085    if ~strcmp('a', lower(varargin{3}))
0086       error('Unknown parameter.');
0087    end
0088    assimetric = 1;
0089   
0090 case 4
0091    error('Too many inputs!')
0092    return
0093 end
0094 
0095 if length(M)==1 
0096    if sum(size(X)>1)>1
0097       M = M*ones(1,ndims(X));
0098    elseif ndims(X)==2 & size(X,1)==1 & size(X,2)>1
0099       M = [0 M];
0100    elseif ndims(X)==2 & size(X,1)>1 & size(X,2)==1
0101       M = [M 0];
0102    end
0103 end
0104 
0105 if length(M)~=ndims(X)
0106    error('Invalid dimensions')
0107 end
0108