change date format in table

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Sara Antonio
Sara Antonio 2017-12-28
编辑： Rena Berman 2024-7-16
I have several txt files with date format set as dd/MM/uuuu hh:mm:ss (e.g 01/06/2008 00:15:00) that I read them into a table. When I convert them into timetable the date mantains in the same format. However when I add rows in the table in a loop, the date format changes into MM/dd/uuuu, and I get this warning: Warning: The DATETIME data was created using format 'MM/dd/uuuu HH:mm:ss' but also matched 'dd/MM/uuuu HH:mm:ss'. To avoid ambiguity, use a format character vector. e.g. '%{MM/dd/uuuu HH:mm:ss}D'
Where do I change the date format as it says in the e.g?
Here is my code:
%Initial empty table
T = timetable(datetime('01/Jan/2000 00:00:00'), NaN, NaN, NaN);
T.Properties.VariableNames = {'SignificantWaveHeight_Hsig_', 'SignificantWavePeriod_Tsig_', 'MeanMagneticDirection'};
for i = 8 %1:numel(allNames)
a = readtable(allNames{i});
c = a(:,{'Received', 'SignificantWaveHeight_Hsig_', 'SignificantWavePeriod_Tsig_', 'MeanMagneticDirection'});
b =table2timetable(c);
TT2 = retime(b,'daily','mean');
T = [T; TT2];
end

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回答（1 个）

Peter Perkins
Peter Perkins 2017-12-28
The warning is coming from readtable, and it's worth paying attention to what it says, and addressing the issue, because that is the root of your problem.
Also, when you concatenate two datetime vectors (which is what's happening when you concatenate T and TT2), the format of the result is the same as the format of the first vector in the concatenation. Look at the format you have used in initializing your timetable.
  2 个评论
Sara Antonio
Sara Antonio 2017-12-28
Thanks for your reply. How do I set the date format then when I use readtable? That is the part I can't do it. My final table instead of 1-jan-2008 to 30-jan-2008 is resulting in:
1-jan; 1-Feb; ... ; 1-Dec, 13-Jan; ... 30-Jan; 1-jan and so on.
How can I work this out because I cannot change the raw data.
Peter Perkins
Peter Perkins 2018-1-5
编辑：Rena Berman 2024-7-16
See the description of the 'Format' parameter in the readtable documentation, which will lead you to the doc for textscan.
If you have a recent version of MATLAB, you can also use detectimportoptions .

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