transfer<-function(a, N=1024)  {
	##a is a vector of filter coefficients
	##N (power of two) is the number of frequencies in [-pi, pi]
	##where the transfer function is calculated
	lambda<-seq(from=-pi, to=pi, length=N)
	temp<-fft(c(a, rep(0, N-length(a))))
	##reorder the values to match the frequencies 
	temp<-c(temp[(N/2):N], temp[1:(N/2-1)])	
	real<-Re(temp)
	imag<-Im(temp)
	gain<-Mod(temp)
	phase<-Arg(temp)
	invisible(return(list("freq"=lambda, "real"=real,"imaginary"=imag, "gain"=gain, "phase"=phase)))
	}