function [beat,tb,xbeat]=fanal(t,x)
%% Carol Lucas
%% Function called to pick out beats (frequency analysis) from vector x
%% Uses simple zero crossing technique.  
%% beat = length of time for the beat
%% tb=time selected for start of beat
%% xvalue at that time

sfill=1;

xmean=mean(x);
x=x-xmean;    %% TAKE MEAN OUT TO GET ZERO CROSSINGS AT MEAN

beat=0*t;
tb(1)=0;
xbeat(1)=xmean;
np=1;
for k=1:length(t)-1
	if and(x(k)<=0,x(k+1)>=0)
		for n=sfill:k
			beat(n)=t(k)-t(sfill);
			end;
			sfill=k;
			tb(np)=t(k);
			xbeat(np)=x(k)+xmean;
			np=np+1;
			end
end