get_dispersion_from_etaoids

get_dispersion_from_etaoids computes dispersion functions (x,px,y,py) at refpts
using the etaoids (E. Forest terminology) which are computed from the one turn map

0001 function disp = get_dispersion_from_etaoids(ring,refpts)
0002 %get_dispersion_from_etaoids computes dispersion functions (x,px,y,py) at refpts
0003 %using the etaoids (E. Forest terminology) which are computed from the one turn map
0004 
0005 for j=1:length(refpts)
0006     k=refpts(j);
0007     if k==1
0008         newring=ring;
0009     else
0010         newring=[ring(k:end);ring(1:k-1)];
0011     end
0012     m66=findm66(newring);
0013     A=amat(m66);
0014     [H1,H2,H3]=find_etaoids(A);
0015     H3(6,6)
0016     disp(:,j) = H3*[0 0 0 0 1 0]';
0017 end