Creating a daily date vector

5 views (last 30 days)
Lejla Latifovic
Lejla Latifovic on 29 Apr 2022
Edited: Lejla Latifovic on 17 May 2022
Hello,
I hope this is a fairly easy question for the community. I have a half hourly datetime vector which I would like to convert to a daily datetime vector. I don't seem to be having any luck. There must be a simple code to do this? Any help would be much appreciated.
Here is an example of my data: date2017 (17520x1 datetime)
date2017 =
'01/01/2017 00:30:01'
'01/01/2017 01:00:01'
'01/01/2017 01:30:01'
'01/01/2017 02:00:01'
'01/01/2017 02:30:01'
'01/01/2017 03:00:01'
'01/01/2017 03:30:01'
'01/01/2017 04:00:01'
'01/01/2017 04:30:01'
'01/01/2017 05:00:01'
'01/01/2017 05:30:01'
'01/01/2017 06:00:01'
'01/01/2017 06:30:01'
'01/01/2017 07:00:01'
'01/01/2017 07:30:01'
'01/01/2017 08:00:01'
'01/01/2017 08:30:01'
'01/01/2017 09:00:01'
'01/01/2017 09:30:01'
'01/01/2017 10:00:01'
'01/01/2017 10:30:01'
'01/01/2017 11:00:01'
'01/01/2017 11:30:01'
'01/01/2017 12:00:01'
'01/01/2017 12:30:01'
'01/01/2017 13:00:01'
'01/01/2017 13:30:01'
'01/01/2017 14:00:01'
'01/01/2017 14:30:01'
I'd like to do this so that I can match it to daily mean values I have for temperature.
I tried this but something went wrong. I ended up with a DateDaily (367x0 timetable) vector, so no date values.
T = table(date2017, 'VariableNames' , {'Date'});
D = table2timetable(T);
DateDaily = retime(D, 'daily');
Thank you!

Accepted Answer

Steven Lord
Steven Lord on 29 Apr 2022
Based on your stated goal, I'd probably store the data in a timetable array and then use retime to change it to a 'daily' timetable.
n = 15;
randomHourVector = randi(6, n, 1); % n random integers between 1 and 6
d = datetime('now') + hours(cumsum(randomHourVector));
x = (1:n).';
tt = timetable(d, x)
tt = 15×1 timetable
d x ____________________ __ 29-Apr-2022 21:32:15 1 30-Apr-2022 00:32:15 2 30-Apr-2022 06:32:15 3 30-Apr-2022 08:32:15 4 30-Apr-2022 11:32:15 5 30-Apr-2022 12:32:15 6 30-Apr-2022 17:32:15 7 30-Apr-2022 20:32:15 8 01-May-2022 02:32:15 9 01-May-2022 04:32:15 10 01-May-2022 08:32:15 11 01-May-2022 09:32:15 12 01-May-2022 13:32:15 13 01-May-2022 15:32:15 14 01-May-2022 16:32:15 15
tt2 = retime(tt, 'daily', @mean)
tt2 = 3×1 timetable
d x ___________ __ 29-Apr-2022 1 30-Apr-2022 5 01-May-2022 12
  7 Comments
Steven Lord
Steven Lord on 29 Apr 2022
The output of cumsum is not going to be suitable for use as an aggregation method in retime. It doesn't reduce a vector of data down to a scalar value like sum and mean do. But if I understand what you want, you can do that using cumsum after the retime call.
n = 15;
randomHourVector = randi(6, n, 1); % n random integers between 1 and 6
d = datetime('now') + hours(cumsum(randomHourVector));
x = (1:n).';
tt = timetable(d, x)
tt = 15×1 timetable
d x ____________________ __ 29-Apr-2022 22:57:36 1 30-Apr-2022 00:57:36 2 30-Apr-2022 03:57:36 3 30-Apr-2022 06:57:36 4 30-Apr-2022 08:57:36 5 30-Apr-2022 11:57:36 6 30-Apr-2022 13:57:36 7 30-Apr-2022 16:57:36 8 30-Apr-2022 19:57:36 9 01-May-2022 00:57:36 10 01-May-2022 03:57:36 11 01-May-2022 05:57:36 12 01-May-2022 09:57:36 13 01-May-2022 11:57:36 14 01-May-2022 15:57:36 15
tt2 = retime(tt, 'daily', @mean)
tt2 = 3×1 timetable
d x ___________ ____ 29-Apr-2022 1 30-Apr-2022 5.5 01-May-2022 12.5
tt2.CumulativeSum = cumsum(tt2.x)
tt2 = 3×2 timetable
d x CumulativeSum ___________ ____ _____________ 29-Apr-2022 1 1 30-Apr-2022 5.5 6.5 01-May-2022 12.5 19
Lejla Latifovic
Lejla Latifovic on 29 Apr 2022
Yes, that is exactly it. Wonderful! Thank you for all of your help, much appreciated.

Sign in to comment.

More Answers (0)

Categories

Find more on Timetables in Help Center and File Exchange

Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!