what was the yearly average value of weight for patient 21079 since 2105?
select avg(chartevents.valuenum) from chartevents where chartevents.icustay_id in ( select icustays.icustay_id from icustays where icustays.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 21079 ) ) and chartevents.itemid in ( select d_items.itemid from d_items where d_items.label = 'admit wt' and d_items.linksto = 'chartevents' ) and strftime('%y',chartevents.charttime) >= '2105' group by strftime('%y',chartevents.charttime)