Timetable - loop through days to check for a condition occurring during midday the day prior to midday of the current day

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Hi all,
I was after some help with my fitbit fitness tracker data. I'm still trying to get my head around timetables (and Matlab in general) so go easy on me!
I have a timetable with a row for each minute (timestamp is in this format: '01-Dec-2019 00:00:00'). The timetable also has several columns of different activity states ('sleep' 'sed' 'lpa' 'mpa' 'vpa') where the value in each cell is either a 1 or 0 depending on the activity state for that minute and the total across the row will always be 1. For example for minute '01-Dec-2019 00:00:00' the columns would look like sleep=1 sed=0 lpa=0 mpa=0 vpa=0 when the participant was asleep during that minute.
Now to deem a day as valid, amongst several conditions, there needs to be any amount of sleep (>=1 rows scored as sleep) between midday of that day and midday of the day prior. So for '01-Dec-2019' to be valid there needs to be at least a single row scored as sleep '30-Nov-2019 12:00:00' and '01-Dec-2019 12:00:00'. I also need to loop this through every day of my dataset (roughly 12 months). I'm looking to write this loop so that the resulting variable is a daily column of logical responses (0 or 1) to the question "is there any sleep from midday yesterday to midday today?".
The start date doesn't matter for now, I will always have a full day prior to my date range of interest to allow for testing this condition.
I hope I've made sense and provided enough detail.

Accepted Answer

Eric Sofen
Eric Sofen on 3 May 2021
As a starting point, take a look at the retime function.
I think the easiest way to do this is create a copy of the timetable, shift the time by 12 hours so that a day's sleep falls within a calendar day.
ttShifted = tt(:,'sleep');
ttShifted.date = ttShifted.date+hours(12);
Then use retime to find the total amount of sleep/day, then figure out if it's more than an hour. Note that this assumes that your data is always once/minute.
ttCountSleep = retime(ttShifted, 'daily', 'sum')
ttValidDay = ttCountSleep.sleep > 60;

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R2021a

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