what was the yearly average value of the lactate of patient 2482?
select avg(labevents.valuenum) from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 2482 ) and labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'lactate' ) group by strftime('%y',labevents.charttime)