// displays a matrix as a gray-level picture

function show_mat(A, orig)
  [n,m] = size(A);
  
  [lhs, rhs]=argn();
  if (rhs==1) then orig=[0,0]; xbasc(); end
  // detect row coded vector instead of a matrix
  if n==1 then A=matrix(A,28,28);  [n,m] = size(A);end
  x = [orig(1):1./(n-1):orig(1)+1];
  y = [orig(2)+1:-1./(m-1):orig(2)];
  ncolor = 255;
  h=graycolormap(ncolor);
  xset('colormap',h);
  grayplot(x,y,A,frameflag=8);
endfunction