samer@0: function Y=rndwindow(X,span,dim,varargin)
samer@3: % rndwindow - get random windows of a signal
samer@0: %
samer@0: % rndwindow :: 
samer@0: %    [Size:[1,E]] ~'E-dimensional signal array',
samer@0: %    L:natural    ~'span of windows to extract',
samer@0: %    D:1..E       ~'dimension to operate along',
samer@0: %    randstate    ~'intial state of rngs'
samer@0: % -> seq [arrset(Size,D,L)] ~'seq of arrays of size L in Dth dimension'.
samer@0: 
samer@37: 	opts=options('state',rndstate,'circular',0,varargin{:});
samer@0: 
samer@0: 	sz=size1(X);
samer@0: 	if nargin<3, dim=length(sz); end
samer@0: 	len=sz(dim);
samer@0: 	ran=[0,span-1];
samer@0: 
samer@0: 	if opts.circular, 
samer@0: 		ithresh=len-span+1;
samer@23: 		Y=map(@exwin_circ,rndzip(@()randnat(len),opts.state));
samer@0: 	else 
samer@23: 		Y=map(@exwin,rndzip(@()randnat(len-span+1),opts.state));
samer@0: 	end
samer@0: 
samer@0: 	function y=exwin(i), y=extract(X,dim,i+ran); end
samer@0: 	function y=exwin_circ(i), 
samer@0: 		if i<=ithresh
samer@0: 			y=extract(X,dim,i+ran);
samer@0: 		else
samer@0: 			y=cat(dim,extract(X,dim,[i,len]),extract(X,dim,[1,span-(1+len-i)]));
samer@0: 		end
samer@0: 	end
samer@0: 	
samer@0: 	function s=strfn(a)
samer@0: 		s=sprintf('rndwindow(%s,%d)',tostring(X),span);
samer@0: 	end
samer@0: end
samer@0: 
samer@0: 	
samer@0: 
samer@0: 
samer@0: 
samer@0: