function unit_square ( row, col, color )
%
%  Draw a unit square, filled with the given color.
%  Square ( 1, 1, 'r' ) is a red square with lower left corner at (0,0)
%  and upper right corner at (1,1).
%
%  The squares are slightly reduced in size so that the gaps between
%  them show up.
%
  abit = 0.05;

  xl = col - 1 + abit;
  xr = col - abit;
  yb = row - 1 + abit;
  yt = row - abit;

  xlist = [ xl, xr, xr, xl ];
  ylist = [ yb, yb, yt, yt ];
  fill ( xlist, ylist, color );

  return
end
