instruction: today what was the heart rate maximum value of patient 1784?
response: SELECT MAX(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 = 1784)) AND chartevents.itemid IN (SELECT d_items.itemid FROM d_items WHERE d_items.label = 'heart rate' AND d_items.linksto = 'chartevents') AND DATETIME(chartevents.charttime, 'start of day') = DATETIME(CURRENT_TIME(), 'start of day', '-0 day')