function y=shiftud(a,n,cs)%SHIFTUD Shift or Circularly Shift Matrix Rows.% SHIFTUD(A,N) with N>0 shifts the rows of A DOWN N rows.% The first N rows are replaced by zeros and the last N% rows of A are deleted.% % SHIFTUD(A,N) with N<0 shifts the rows of A UP N rows.% The last N rows are replaced by zeros and the first N% rows of A are deleted.% % SHIFTUD(A,N,C) where C is nonzero performs a circular% shift of N rows, where rows circle back to the other% side of the matrix. No rows are replaced by zeros.%% D.C. Hanselman, University of Maine, Orono ME 04469% 1/24/95% Copyright (c) 1996 by Prentice-Hall, Inc. if nargin<3,cs=0;end	% if no third argument, default is Falsecs=cs(1);				% make sure third argument is a scalar[r,c]=size(a);			% get dimensions of inputdn=n>=0;				% dn is true if shift is downn=min(abs(n),r);		% make sure shift amount is less than matrix rowsif n==0|(cs&n==r)					% simple no shift case	y=a;elseif ~cs&dn						% no circular and down	y=[zeros(n,c); a(1:r-n,:)];elseif ~cs&~dn						% no circular and up	y=[a(n+1:r,:); zeros(n,c)];elseif cs&dn						% circular and down	y=[a(r-n+1:r,:); a(1:r-n,:)];elseif cs&~dn						% circular and up	y=[a(n+1:r,:); a(1:n,:)];end