function Am=appendmirror(A)
%APPENDMIRROR append the mirrored matrix rows before and after
%   Am = APPENDMIRROR(A) build to the rows of A
%   the left and right A mirrors, one before and the other after
%   the resulting array/matrix length is 3*length(A)
%   Useful for filtering or resampling functions
%   
%   Author(s): F. Patanč, 2000

l=size(A,1);
Afl=flipud(A);
Abeg=repmat(2*A(1,:),[l,1])-Afl;
Aend=repmat(2*A(end,:),[l,1])-Afl;
Am=[...
        Abeg(1,:);...
        Abeg((1:(end-1)),:);...
        A;...
        Aend((2:end),:);...
        Aend(end,:)...
    ];