function [sig,sig2,osig,msig,tsig,tau]=avar(y,tau0)
  % function [sig,sig2,osig,msig,tsig,tau]=avar(y,tau0)
  % INPUTS:
  %  y = signal
  %  tau0 = sampling period (s)
  %
  % OUTPUTS:
  % sig =  N samples STD DEV
  % sig2 = Normal Allan STD DEV, 2 samples STD DEV.
  % osig = Sigma(y)(tau) = Allan Standard Deviation with Overlapping estimate
  % msig = Modified Allan Standard Deviation
  % tsig = Time Allan Standard Deviation
  % tau = measurement time (s).
  %
  % Copyright Alaa MAKDISSI 2003
  % free for personal use only.
  
  s=[];
  x=[];
  n=length(y);
  jj=floor( log((n-1)/3)/log(2) );
  
  for j=0:jj
      fprintf('.');
      m=2^j;
      tau(j+1)=m*tau0;
      D=zeros(1,n-m+1);
      for i=1:n-m+1
          D(i)=sum(y(i:i+m-1))/m;
      end
      %N sample
      sig(j+1)=std(D(1:m:n-m+1));
      %AVAR
      sig2(j+1)=sqrt(0.5*mean((diff(D(1:m:n-m+1)).^2)));
      %OVERAVAR
      z1=D(m+1:n+1-m);
      z2=D(1:n+1-2*m);
      u=sum((z1-z2).^2);
      osig(j+1)=sqrt(u/(n+1-2*m)/2);
     
      %MVAR
      u=zeros(1,n+2-3*m);
      for L=0:n+1-3*m
          z1=D(1+L:m+L);
          z2=D(1+m+L:2*m+L);
          u(L+1)=(sum(z2-z1))^2;
      end
     
      uu=mean(u);
      msig(j+1)=sqrt(uu/2)/m;
     
      %TVAR
      tsig(j+1)=tau(j+1)*msig(j+1)/sqrt(3);
     
  end