Redo Generated per day

SELECT trunc(first_time) DAY,
count(*) NB_SWITCHS,
trunc(count(*)*log_size/1024) TOTAL_SIZE_KB,
to_char(count(*)/24,'9999.9') AVG_SWITCHS_PER_HOUR
FROM v$loghist,
(select avg(bytes) log_size from v$log) GROUP BY trunc(first_time),log_size
order by 1 desc