how to calculate hourly averages?

I convertued my file to a csv, then used the following code to try and get hourly averages:

writematrix(NTU,'M.csv');

T1 = readtable('M.csv');

TT1 = table2timetable(T1,'RowTimes',NTU);

TT1 = retime(TT1, 'hourly','mean');

Am I using table2timetable wrong?

[Steven Lord]

What leads you to think that you're using table2timetable incorrectly?

• Do you receive warning and/or error messages? If so the full and exact text of those messages (all the text displayed in orange and/or red in the Command Window) may be useful in determining what's going on and how to avoid the warning and/or error.
• Does it do something different than what you expected? If so, what did it do and what did you expect it to do?
• Did MATLAB crash? If so please send the crash log file (with a description of what you were running or doing in MATLAB when the crash occured) to Technical Support so we can investigate.

[Laura]

Error using table2timetable:

"Row times must be specified as variable name or index, or as datetime or duration vector."

[Steven Lord]

Okay. So what data type is NTU? Is it the name of a variable in the table T1, is it a datetime or duration vector, or is it something else?

Run this command immediately before your table2timetable call and show us what it displays, please.

whos NTU

[Laura]

NTU 2856x1 22848 double

[Steven Lord]

So what do the values in NTU represent? Seconds since an epoch, days since an epoch, yyyymmdd, etc.?

Use those as inputs to datetime or duration (possibly with 'ConvertFrom' and the appropriate option for what your data represents) then use the datetime or duration array that call returns as your RowTimes. For example:

dt1 = datetime(19850621, 'ConvertFrom', 'yyyymmdd') % June 21, 1985 or

dt1 = datetime
   21-Jun-1985

dt2 = datetime(1e8, 'ConvertFrom', 'epochtime') % 1e8 seconds since Jan 1, 1970

dt2 = datetime
   03-Mar-1973 09:46:40

datetime(1970, 1, 1) + seconds(1e8)

ans = datetime
   03-Mar-1973 09:46:40