How to separate and order timetable data by year

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Joe Wheeler
Joe Wheeler on 15 Nov 2021
Edited: Adam Danz on 17 Nov 2021
data = readtable('USA_SITE_004_final.txt'); %import text file and present as table
data_nan = standardizeMissing(data, -999); %return '-999' values as 'NaN'
hourly_temp_rain_sm = data_nan(:, [1 5 11 26]); %extract key variables
TT = table2timetable(hourly_temp_rain_sm); %form timetable
daily_temp_rain_sm = retime(TT, 'daily', 'mean'); %retime data to obtain daily averages
daily_sm = daily_temp_rain_sm(:,3);
Hi, i have created a timetable and retimed soil moisture data here to obtain daily averages for a period of several years. I now want to be able to obtain a metric for each year and to do this i will need to separate the data into years, keeping the daily averages each year. I hope that makes sense and thank you in advance for any help.

Answers (1)

Adam Danz
Adam Danz on 15 Nov 2021
Edited: Adam Danz on 15 Nov 2021
> I now want to be able to obtain a metric for each year and to do this i will need to separate the data into years, keeping the daily averages each year.
You can use retime with yearly intervals. By storing this in a different variable, you can also keep the daily values.
dt = datetime(1999,1,1) + days(0:1:2000)';
rainfall = rand(numel(dt),1);
TT = timetable(dt, rainfall) % Daily rainfall
TT = 2001×1 timetable
dt rainfall ___________ ________ 01-Jan-1999 0.09073 02-Jan-1999 0.82922 03-Jan-1999 0.68411 04-Jan-1999 0.15243 05-Jan-1999 0.47396 06-Jan-1999 0.084376 07-Jan-1999 0.50433 08-Jan-1999 0.65501 09-Jan-1999 0.47188 10-Jan-1999 0.29966 11-Jan-1999 0.90719 12-Jan-1999 0.51547 13-Jan-1999 0.47611 14-Jan-1999 0.6801 15-Jan-1999 0.015343 16-Jan-1999 0.56246
yearlyTT = retime(TT,'yearly','mean') % yearly avg
yearlyTT = 6×1 timetable
dt rainfall ___________ ________ 01-Jan-1999 0.52045 01-Jan-2000 0.51869 01-Jan-2001 0.49597 01-Jan-2002 0.50299 01-Jan-2003 0.50966 01-Jan-2004 0.47196
Note that the aggregate method can be a function handle if your metric is not a built-in option. See doc retime for more info.
  6 Comments
Adam Danz
Adam Danz on 16 Nov 2021
What Matlab release are you using?
I'm assuming daily_sm.DT contains datetime values. Does year(daily_sm.DT) throw an error?
Or maybe you have a variable named "year" which is preventing use of the function of the same name.

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