# Core CIF Dictionary version 2.3

# _refine_ls_class_R_I_factor

### Name

`'_refine_ls_class_R_I_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(I) for the
reflections judged significantly intense (i.e. satisfying the
threshold specified by _reflns_threshold_expression) and
included in the refinement.
This is most often calculated in Rietveld refinements
of powder data, where it is referred to as R~B~ or R~Bragg~
sum | I(obs) - I(calc) |
R(I) = ------------------------
sum | I(obs) |
I(obs) = the net observed intensities
I(calc) = the net calculated intensities
and the sum is taken over the reflections of this class.

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