Weighted residual factor wR for reflections that satisfy the
resolution limits established by _refine.ls_d_res_high and
_refine.ls_d_res_low and the observation limit established by
_reflns.observed_criterion, and that were used as the test
reflections (i.e. were excluded from the refinement) when the
refinement included the calculation of a 'free' R factor.
Details of how reflections were assigned to the working and
test sets are given in _reflns.R_free_details.
( sum|w |Yobs - Ycalc|2| )1/2
wR = ( ---------------------------- )
( sum|w Yobs2| )
Yobs = the observed amplitude specified by
Ycalc = the calculated amplitude specified by
w = the least-squares weight
sum is taken over the specified reflections