function [ phaseABCY ] = Yf2p( fs0,fs1,fs2 )
[r,c]=find(fs1);
a=exp(1j*2*pi/3);
Tp2f=1/3*[1 1 1;
    1 a a^2;
    1 a^2 a];
Tf2p=inv(Tp2f);
%
% Tf2p=[1 1 1;
%     1 a^2 a;
%     1 a a^2];
busNum=size(fs0,1);
phaseABCY=sparse(3*busNum,3*busNum);
for I=1:length(r)
    v0=fs0(r(I),c(I));
    v1=fs1(r(I),c(I));
    v2=fs2(r(I),c(I));
    pabc=Tf2p*diag([v0,v1,v2])*Tp2f;
    [pr,pc,pv]=find(pabc);
    phaseABCY=phaseABCY+sparse(pr+3*(r(I)-1),pc+3*(c(I)-1),pv,3*busNum,3*busNum);
end
end