function a = matVtoI(nv,nc,con,R)
a = zeros(nv,nv);
for ic=1:nc
    k1=con(ic,1);
    k2=con(ic,2);
    aux=1/R(ic);
    a(k1,k1)=a(k1,k1)+aux;
    a(k2,k2)=a(k2,k2)+aux;
    a(k1,k2)=a(k1,k2)-aux;
    a(k2,k1)=a(k2,k1)-aux;
end
return
end