function [a,b]=ffill(x,ixc,y)
// Copyright (C) 2001 Michel Juillard
// 
 
xc = size(x,1);
 
if y==[] then
  b = [ixc;0];
  a = [x,zeros(size(x,1),1)];
else
  yc = size(y,1);
  b = [ixc;yc];
   
  if xc>yc then
    a = [x,[y;zeros(xc-yc,size(y,2))]];
  elseif yc>xc then
    a = [[x;zeros(yc-xc,size(x,2))],y];
  else
    a = [x,y];
  end
   
end
 
// 2001/09/1 MJ corrected for absent lags