function B = Shift(A,s);
% B = Shift(A,s);
%
% Circularly shift the rows of matrix A by s entries.
% Positive s shifts right, while negative s shifts left.
% If s exceeds the matrix dimensions, modulo addressing is
% applied.
%
% St.Weiss, University of Strathclyde, 16.7.1997

[m,n] = size(A);
s = mod(s,n);

B = [A(:,n-s+1:n) A(:,1:n-s)];