function [W,d,r1,r2,alpha,r]=pbfx(X1,X2,X)
miu1=mean(X1,2);
miu2=mean(X2,2);
miu=(miu1+miu2)/2;
[m,n1]=size(X1);
[m,n2]=size(X2);
 for i=1:m
     ss1(i,:)=X1(i,:)-miu1(i); 
     ss2(i,:)=X2(i,:)-miu2(i);  
 end
 
s1=ss1*ss1';
s2=ss2*ss2';
V=(s1+s2)/(n1+n2-2);
W(1:m)=inv(V)*(miu1-miu2);
W(m+1)=(-miu)'*inv(V)*(miu1-miu2);
d=(miu1-miu2)'*inv(V)*(miu1-miu2);
r1=W(1:m)*X1+W(m+1);
r2=W(1:m)*X2+W(m+1);
r1(r1>0)=1;
r1(r1<0)=2;
r2(r2>0)=1;
r2(r2<0)=2;
num1=n1-length(find(r1==1));
num2=n2-length(find(r2==2));
alpha=(num1+num2)/(n1+n2)
r=W(1:m)*X+W(m+1);
r(r>0)=1;
r(r<0)=2;