samer@0: % afilter - Linear filter arrow
samer@0: %
samer@0: % afilter :: 
samer@0: %    [[P]] ~'filter B coefficients',
samer@0: %    [[Q]] ~'filter A coefficients',
samer@0: % -> arrow({[[N]]},{[[N]]},[[O]]).
samer@0: %
samer@0: % The arrow afilter(B,A) is equivalent to using filter(B,A,X)
samer@0: % on a signal in an array.
samer@0: 
samer@0: function o=afilter(b,a,zi)
samer@0: 
samer@0: 	if nargin<3, zi=[]; end
samer@0: 	o = loop(@filt,@(s)zi);
samer@0: 	function [y,z]=filt(x,z)
samer@0: 		[y,z]=filter(b,a,x,z);
samer@0: 	end
samer@0: end