function abcd(L)
%ABCD produces a gray "checkerboard" plot of the given n1-by-n2 matrix L.
% Unlike the PCOLOR function, ABCD uses the last row and column of
% the matrix L.

%          last updated on March 31, 2001 by S. H. Zak

n1=size(L,1);
n2=size(L,2);
u=ones(n1,1);
v=ones(1,n2+1);
La=[L u;v];
pcolor(La)
colormap(gray)
axis('ij')
axis('square')
axis off