samer@3: function y=filter(a,b,x,z,dim)
samer@3: % filter - filter for sequences of array
samer@3: %
samer@3: % filter :: [[P]], [[P]], seq [Size], [[P]], D:natural -> seq [Size].
samer@3: % filter :: [[P]], [[P]], seq [Size], [[P]]  -> seq [Size].
samer@3: % filter :: [[P]], [[P]], seq [Size]  -> seq [Size].
samer@3: %
samer@3: % filtering is done along Dth dimension of the array (default=1)
samer@3: 
samer@23: if isempty(x), y=nil; return; end
samer@3: if nargin<5, 
samer@3: 	dim=find(size(x)>1,1);
samer@3: 	if isempty(dim), dim=1; end
samer@3: 	if nargin<4, z=[]; end
samer@3: end
samer@3: 
samer@25: y = mapaccum(@(x1,z1)filter(a,b,x1,z1,dim),z,x);