Creating a daily date vector
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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!
采纳的回答
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)
tt2 = retime(tt, 'daily', @mean)
7 个评论
Lejla Latifovic
2022-4-29
Steven Lord
2022-4-29
Please show us the outputs of these commands:
head(D)
head(DateDaily)
Lejla Latifovic
2022-4-29
编辑：Lejla Latifovic
2022-4-29
Steven Lord
2022-4-29
Your table T has just the datetime data in it. table2timetable converts the first date or time variable from your table into the RowTimes of the timetable and converts all the other table variables into timetable variables. But you don't have any other table variables so the result is an empty timetable.
Put your datetime data and the associated data that you want to "match it to daily mean values I have for temperature" into the table T and convert that into a timetable. Note that tt in my example has both datetime data (the d variable) and non-datetime data (x.)
Lejla Latifovic
2022-4-29
编辑：Lejla Latifovic
2022-5-17
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)
tt2 = retime(tt, 'daily', @mean)
tt2.CumulativeSum = cumsum(tt2.x)
Lejla Latifovic
2022-4-29
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