**Definition:**

Residual factor R 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 working reflections (i.e. were included in 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. _refine.ls_R_factor_obs should not be confused with _refine.ls_R_factor_R_work; the former reports the results of a refinement in which all observed reflections were used, the latter a refinement in which a subset of the observed reflections were excluded from refinement for the calculation of a 'free' R factor. However, it would be meaningful to quote both values if a 'free' R factor were calculated for most of the refinement, but all of the observed reflections were used in the final rounds of refinement; such a protocol should be explained in _refine.details. sum|F~obs~ - F~calc~| R = --------------------- sum|F~obs~| F~obs~ = the observed structure-factor amplitudes F~calc~ = the calculated structure-factor amplitudes sum is taken over the specified reflections

**Type:** float

**Mandatory item:** no

The permitted range is [0.0, infinity)

**Related item: **_refine.ls_wR_factor_R_work (alternate)

**Category:** refine

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