以下的这个程序是用来做方差比检验的m-file 大家看看有问题么
我跑出来的结果只有一个数，而我要得到两个数的，即同方差和异方差下的方差比

function [VR,Zk,Zhk]=vrt_full(x,k)
%
% Syntax: [vr,zk,zhk]=vrt(x,k)
%
% Calculates the Variance Ratio Test (VR Test) of a time series x, with
% and without the heteroskedasticity assumption.
% input  : x is a vector of time serie (observed prices)
%          k is a scalar
% output : VR is the value of the VRTest
%          Zk is the homoscedastic statistic of the variance ratio
%          Zhk is the heteroscedastic statistic of the variance ratio
%
x=xlsread('D:\A股\数\book1.xls');
k=2;
rt1=diff(x); % one period rate of return

T=length(rt1);
i=1:T-k+1;
M=zeros(T-k+1,k);
for j=1:k,
    M(:,j)=i+j-1;
end
rtk=sum(rt1(M'));  % k period rate of return

moy=mean(rt1);
v=var(rt1);
m=k*(T-k+1)*(1-k/T);
VR=1/m*sum((rtk-k*moy).^2)/v; % Variance ratio statistic

Zk=sqrt(T)*(VR-1)*(2*(2*k-1)*(k-1)/(3*k))^(-.5); % homoscedastic statistic

j=1:k-1;
vec1=(2/k*(k-j)).^2;
rst=(rt1-moy).^2;
aux=zeros(1,k-1);
for i=1:k-1,
   aux(i)=rst(i+1:T)'*rst(1:T-i);
end
vec2=aux/((T-1)*v)^2;
Zhk=(VR-1)*(vec1*vec2')^(-.5); % heteroscedastic statistic