Subset timetable based on datetime values
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Hello, I have a timetable which has datetime values incrementing in ten minute intervals over a year, e.g.:
DateTime BoatCount PV
___________________ _________ __
29.05.2019 10:30:00 1 0
29.05.2019 10:40:00 0 0
29.05.2019 10:50:00 0 0
29.05.2019 11:00:00 0 0
29.05.2019 11:10:00 0 0
29.05.2019 11:20:00 0 0
29.05.2019 11:30:00 0 0
29.05.2019 11:40:00 0 0
I want to subset this data so I am only including values recorded in daylight hours e.g. 0600-2030. How do I subset the data by datetime values? Something like...
daylighthours=TT2(TT2.DateTime=='29/05/2019 06:00:00' : '29/05/2019 20:30:00')
but which would cycle through each day of the year
采纳的回答
Adam Danz
2020-3-17
Here's a demo that determines which rows of a timetable have times that are between two values.
% Create a demo timetable
TT = timetable((datetime('now') - minutes(0:248:60000))', rand(242,1));
% Get time-part (in duration format)
dur = TT.Time - dateshift(TT.Time, 'start', 'day');
% Define sunrise and sunset
sunrise = duration(6,30,0); % 6:00
sunset = duration(20,30,0); % 20:30
% Determine which times are between sunrise and sunset
idx = dur >= sunrise & dur <= sunset;
% Isolate rows of timetable that are during daylight
TT(idx,:)
Note: Sunrise and sunset are not fixed every day. A better approach would be to us a vector of sunrise and sunset times the same length as the datetime column and to determine whether each row is between those associated sunrise/sunset values.
3 个评论
Akira Agata
2020-3-18
+1
To get time-part in duration format, you can also do that using timeofday function, like:
% Get time-part (in duration format)
dur = timeofday(TT.time);
Louise Wilson
2020-3-18
Thanks, @Akira Agata
@Louise Wilson , sunrise and sunset times not only depend on time-of-year but also on location. You could either search for and download those values or you may be able to compute them.
Update, here's an algorithm to follow
Update 2, Loren has just posted a blog where this algorithm is demonstrated within a GIF image.
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