**Definition:**

For each reflection class, the residual factor R(F^2^) 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.

**Type:** float

**Mandatory item:** no

The permitted range is [0.0, infinity)

**Category:** reflns_class

Copyright © 2005 International Union of Crystallography