function y = padt(x, n, val)%y = padt(x, n, val)% Pad a matrix x on the top to length n with value val(0)% The empty matrix is assumed to be have 1 empty columnif nargin < 3    val = 0;endy = [ val( ones( n-size(x,1), max(1,size(x,2)) ) ); x ];