function [C1,C,Cf,px,py,pz,bianhao]=topu(cab_num,cab_n,cab_i,cab_j,nfix_n,nodefix,nodenum,node_no,fx,fy,fz)

C1(1,1)=0;
for i=1:1:cab_num
    for j=1:1:nodenum
        if cab_i(i)==node_no(j,1)
            a=j;
        elseif cab_j(i)==node_no(j,1)
            b=j;
        end
    end
    C1(i,a)=1;     %這里如果取成C1(cab_n(i),cab_i(i))的話，如果數據文件中cab的編號不連續的話，則矩陣變大
    C1(i,b)=-1;
end
C1;
%提取內部拓撲矩陣Cl和外部拓撲矩陣Cfl
nfix_n(nodefix+1)=-1;
j=1;m=1;n=1;
for i=1:1:nodenum
    if node_no(i,1)==nfix_n(j,1)
        Cf(:,m)=C1(:,i);
        m=m+1;
        j=j+1;
    else
        C(:,n)=C1(:,i);
        px(n,1)=fx(i,1);
        py(n,1)=fy(i,1);
        pz(n,1)=fz(i,1);
        nfree_n(n,1)=node_no(i,1);
        n=n+1;
    end
end
nfix_n(nodefix+1,:)=[];
m=0;n=0;
C1=[C,Cf];
bianhao=[nfree_n',nfix_n']';
%自由節點的荷載向量[fx,fy,fz]'