(1) Twissring.m or atsummary.m; fitchrom2.m; tunechrom.m 

call linopt.m, then 
Use the 4D one turn map.
findm44() 



For ThomX ring:  CDR_017_072_r56_02_sx_Dff_corrSX_BPMIP.m

tune_DDP =

   3.174924939207250   1.719870195003575

DDP =1e-8

tune =

   3.174924939041714   1.719870195095099


(tune_DDP-tune)/DDP

ans =

   0.016553558523924  -0.009152345548102


(2) modelchro.m & modeltune.m & gettune.m & steptune.m

   Use the 6D order transfer matrix findm66.m

For ThomX ring:  CDR_017_072_r56_02_sx_Dff_corrSX_BPMIP.m

FracTune1 =

   0.174925870391515
   0.719871470894530

FracTune0 =

   0.174925868824909
   0.719871468757788

DeltaRF =

     1.000000000000000e-07

Chro = (FracTune1 - FracTune0) / DeltaRF
     =  0.015666058728048
        0.021367424496432
Chro = (-MCF * RF0) * Chro
     = -0.107062428651483
       -0.146025774595083


(3) Measchro.m
 
    call gettune.m, then modeltune.m, then use findm66.m


 use the polynominal fit, dp = 1e-5



The fitted chromaticity are also -0.10616 -0.148526

The chromaticity from measchro.m & modelchrom.m are slightly different.