ruby on rails - Grouping by 4 Hours Intervals -


i'm trying average of data have in 4 hours intervals, app in ruby on rails, don't know if should write postgresql query or in model of application, nor don't know how in either. simple version of model this:

id    heart_rate    timestamp

i need 1 hour, , 1 day interval know how that, on sql side @ least:

select avg(heart_rate), to_char(timestamp, 'yyyy-mm-dd') ts vital_signs group ts order ts asc;

24 hrs / 4 = 6 segments.

convert date hours, integer division (div). give 0-5 numbers. each remainder representing segment.

this example mysql (and not rails), replace div (integer division function of mysql) postgress equivalent.

select      avg(heart_rate), hour(timestamp) div 4, count(*)      vital_signs group      date(timestamp),      hour(timestamp) div 4;

you can group on date seperately, per day getting avg. results.

you can execute sql directly within rails via:

activerecord::base.connection.execute "<sql>"

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