Copyright (C) 2001 Michel Juillard

 Fast hpfiltering:

 [c,t]=hpfast(y,lambda)

 Inputs:

 y:    vector (nx1) containing the series you wish to filter
 lambda: smoothing parameter (default: quarterly 1600)

 Outputs:
 
 c:   Cyclical component (deviations from trend)
 t:   Trend component