% [xl,xlf] = phxl(x,xs,al,pl,xli)
function [xl,xlf] = phxl(x,xs,al,pl,xli)

N = lge(x);
x = abs(x);
xl(1) = xli;

for n = 2:N,
  if(xs(n) > pl*xl(n-1))
    xl(n) = xl(n-1);
  else
    xl(n) = al*x(n) + (1-al)*xl(n-1);
  end;
end;
xlf = xl(N);