# Core CIF Dictionary version 2.3

# _refine_ls_class_R_Fsqd_factor

### Name

`'_refine_ls_class_R_Fsqd_factor'`
**Category:** refine_ls_class

**Data type:** numb

**Must** appear in a looped list
containing `'_refine_ls_class_code'`

**Enumeration range:** 0.0 -> infinity

### 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 _refine_ls_class_d_res_high and _refine_ls_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.

**Copyright © 2003 International Union of Crystallography**
IUCr Webmaster