pivot.m

various matlab programs to slove various problems

function [Pk,Qk]=pivot(A,k,n)
[y,i]=max(abs(A(k:n,k:n)));  
[piv,jpiv]=max(y);
ipiv=i(jpiv);   
jpiv=jpiv+k-1;   
ipiv=ipiv+k-1;
Pk=eye(n); 
Pk(ipiv,ipiv)=0; 
Pk(k,k)=0; 
Pk(k,ipiv)=1; 
Pk(ipiv,k)=1;
Qk=eye(n); 
Qk(jpiv,jpiv)=0; 
Qk(k,k)=0; 
Qk(k,jpiv)=1; 
Qk(jpiv,k)=1;
return