###############

#1. filtfiltx (Roman Murelka)
   #this is an emulation of Matlab filtfilt (as R filtfilt executes a little differently. See http://www.climateaudit.org/?p=4038#comment-304170

   filtfiltx = function( b, a, x = NULL ) {
	if (is.null(x)) { x = a
	a = b$a
	b = b$b }
	len = length(x)
	nfilt = max(length(b),length(a))
	nfact = 3*(nfilt-1) # padding size
	if (len <= nfact) stop("Data must have length more than 3 times filter order.") # Not enough data
	b = c(b, rep(0,nfilt))[1:nfilt] # zero-pad shorter of b and a
	a = c(a, rep(0,nfilt))[1:nfilt] # ditto
	y = c(2*x[1]-rev(x[2:(nfact+1)]), x, 2*x[len]-rev(x[(len-nfact):(len-1)]))
	y = rev(y[1] + filter(b,a,y-y[1]))
	y = rev(y[1] + filter(b,a,y-y[1]))
	y[(nfact+1):(len+nfact)] }