For each reflection class, the residual factor R(F2) calculated
on the squared amplitudes of the observed and calculated
structure factors for the reflections judged significantly
intense (i.e. satisfying the threshold specified by
_reflns.threshold_expression) and included in the refinement.
The reflections also satisfy the resolution limits established
by _reflns_class.d_res_high and _reflns_class.d_res_low.
sum | F(obs)2 - F(calc)2 |
R(Fsqd) = -------------------------------
sum F(obs)2
F(obs)2 = squares of the observed structure-factor amplitudes
F(calc)2 = squares of the calculated structure-factor
amplitudes
and the sum is taken over the reflections of this class.