RING=esrf();
ringpara(RING)
indS=find( atgetcells( RING, 'Class', 'Sextupole' ));
s00=findspos(RING, 1:length(RING)+1);

[bd, par]=atx(RING,0,1:length(RING));
emits=par.modemittance;

RING1 = RING;

%%%%% misalign sextupoles to represent machine imperfections
rng(123456);
dxs = 100e-6 * randn([length(indS),1]);
dys = 100e-6 * randn([length(indS),1]);

RING1=atsetshift( RING1, indS, dxs, dys);

[bd1, par1]=atx(RING1,0,1:length(RING1));
emits1=par1.modemittance;
fprintf('%.4e ',emits1);fprintf('\n');

nlen=length(RING1);
nspace=20;
results=zeros([length(1:nspace:nlen), 7]);
for ind = 1 : nspace : nlen 
    %%%% rotate and start the lattice at ind-th element
    RING2  =  [ RING1(ind:end,1); RING1(1:ind-1,1)];
    [bd2, par2]=atx(RING2,0,1:length(RING2));
    emits2=par2.modemittance;
    demitsratio=(emits2-emits1)./emits1;
    results((ind-1)/nspace+1, :) = [s00(ind), demitsratio, emits2];
    fprintf('%.4e ',results((ind-1)/nspace+1, :));fprintf('\n');
end

figure(1);
plot(results(:,1),results(:,2),'b*');
hold on;
plot(results(:,1),results(:,3),'ro');
legend('dex/ex0','dey/ey0');

save('./esrf_emits.txt','results','-ascii');