function k=peak(x)    
%author lucky zhang
%copyright 2005.6.21
%
[n,T] = size(x);
x = x - mean(x')'*ones(1,T);% Remove mean


    k4=mean(x.^4);
    k2=mean(x.^2);
    k=k4/(k2^2)-3;
   k=sign(k);