Average of variables in timetable belonging to the same day over several years

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Ziad Sari El Dine
Ziad Sari El Dine 2022-8-24
评论： Ziad Sari El Dine 2022-8-25
Hello, I have a timetable, TT(681-by-19), with unevenly spaced daily data from 2010 to 2020 and 19 variables (there might be days that do not occur every year in addition to gaps where entire months are missing). I want to calculate the mean of the variables that correspond to the same day throughout the different years. For example I want to calculate the mean of each of the 19 variables that correspond to 25-oct 2010, 25-oct 2011, ..., 25-oct 2020 and so on for the different dates. That way I would have each unique day-month occurring only once in the output.
Note: I also have the dates seperately as a datetime array and as a numeric array in the form of yyyymmdd (681-by-1) and the 19 variables in a numeric array (681-by-19), if there is a simpler method without the use of the timetable.
Thanks for any assistance.

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采纳的回答

Peter Perkins
Peter Perkins 2022-8-25
Ran in:
Ziad, it seems that "dayofyear" is using "serial day number of year", and as you found, is lumping 29-Feb's with the non-leap 1-Mar's, etc. What you want is to group by month/day. If you use the month and day of month as grouping vars, you get what you want:
dt = [datetime(2012,2,27:31) ...
datetime(2013,2,27:30) ...
datetime(2014,2,27:30) ...
datetime(2015,2,27:30) ...
datetime(2016,2,27:31)]';
x = dt.Day;
tt = timetable(x,RowTimes=dt)
tt = 22×1 timetable
Time x ___________ __ 27-Feb-2012 27 28-Feb-2012 28 29-Feb-2012 29 01-Mar-2012 1 02-Mar-2012 2 27-Feb-2013 27 28-Feb-2013 28 01-Mar-2013 1 02-Mar-2013 2 27-Feb-2014 27 28-Feb-2014 28 01-Mar-2014 1 02-Mar-2014 2 27-Feb-2015 27 28-Feb-2015 28 01-Mar-2015 1
tt.Month = string(month(tt.Time,"name"));
means = 5×3 table
dayofyear_Time GroupCount mean_x ______________ __________ ______ 58 5 27 59 5 28 60 5 12.2 61 5 1.6 62 2 2
tt.Day = day(tt.Time,"dayofmonth");
means = groupsummary(tt,["Month" "Day"],"mean","x")
means = 5×4 table
Month Day GroupCount mean_x __________ ___ __________ ______ "February" 27 5 27 "February" 28 5 28 "February" 29 2 29 "March" 1 5 1 "March" 2 5 2

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Cris LaPierre
Cris LaPierre 2022-8-24

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