A tibble object with 1 row for each subject, a column for subject id and
a column for ADRR values is returned. `NA` glucose values are
omitted from the calculation of the ADRR values.
ADRR is the average sum of HBGI corresponding to the highest glucose
value and LBGI corresponding to the lowest glucose value for each day,
with the average taken over the daily sums. If there are no high glucose or
no low glucose values, then 0 will be substituted for the HBGI value or the
LBGI value, respectively, for that day.