def get_rdts(madx: Madx, order: int = 4, file: Union[Path, str] = None) -> tfs.TfsDataFrame:
"""
INITIAL IMPLEMENTATION CREDITS GO TO JOSCHUA DILLY (@JoschD).
Calculate the RDTs via PTC_TWISS.
Args:
madx (cpymad.madx.Madx): an instanciated cpymad Madx object.
order (int): maximum derivative order (only 0, 1 or 2 implemented in PTC). Defaults to `2`.
file (Union[Path, str]): path to output file. Default `None`
Returns:
A TfsDataframe with results.
"""
logger.info(f"Entering PTC to calculate RDTs up to order {order}")
madx.ptc_create_universe()
logger.trace("Creating PTC layout")
madx.ptc_create_layout(model=3, method=4, nst=3, exact=True)
# madx.ptc_create_layout(model=3, method=6, nst=1) # from Michi
logger.trace("Incorporating MAD-X alignment errors")
madx.ptc_align() # use madx alignment errors
# madx.ptc_setswitch(fringe=True) # include fringe effects
logger.debug("Executing PTC Twiss")
madx.ptc_twiss(icase=6, no=order, normal=True, trackrdts=True)
madx.ptc_end()
logger.debug("Extracting results to TfsDataFrame")
dframe = tfs.TfsDataFrame(madx.table.twissrdt.dframe())
dframe.columns = dframe.columns.str.upper()
dframe.NAME = dframe.NAME.str.upper()
if file:
logger.debug(f"Exporting results to disk at '{Path(file).absolute()}'")
tfs.write(file, dframe)
return dframe
