              Residual factor R(I) 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, calculated on the estimated\
               reflection intensities.\
\
               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\
\
               sum is taken over the specified reflections