how to use datetime(datestr)

Dear all, I tried to convert the matlab serial dates (vector) back to a date string . I use matlab2016b. The data and codein the attached file.

And the error is:

Could not recognize the format of the date/time text. You can specify a format character vector using the 'InputFormat' parameter.

If the date/time text contain day, month, or time zone names in a language foreign to the 'zh_CN' locale, those might not be

recognized. You can specify a different locale using the 'Locale' parameter.

Error in test (line 2)

Time = datetime(datestr((DATA(:,1)+datenum('12/31/1899','mm/dd/yy'))));time_num is a vector of serial dates. I have attached the file please.

Thank you very much!

Answer 1

[Walter Roberson]

Do not try to mix serial data numbers and datetime objects.

You can skip most of your problems.

t = readtable('data.xlsx');
Time = t{:,1};

Time will already be in datetime format, having been automatically converted from Excel date format.

[zhize lee]

Thank you very much. But how can fix it without the applied error.

[Walter Roberson]

That is the code. No datestr() or anything like that are needed. After the two lines I gave, Time will be a column vector of datetime objects

t =

  998×12 table

       Var1        CPIAUCSL    DSPIC96     INDPRO     LNS13023653    PAYEMS      PCE       PCEPI     PCEPILFE    UNRATE    gz_spread      ebp  
    ___________    ________    _______    ________    ___________    ______    _______    _______    ________    ______    _________    _______

    01-Jan-1947      21.48         NaN     14.0679         NaN        43535        NaN        NaN        NaN       NaN         NaN          NaN
    01-Feb-1947      21.62         NaN      14.151         NaN        43557        NaN        NaN        NaN       NaN         NaN          NaN
    01-Mar-1947         22         NaN     14.2341         NaN        43607        NaN        NaN        NaN       NaN         NaN          NaN

and so on.

[zhize lee]

the following code need the datestr()

[Walter Roberson]

The code you posted has two lines. There are no following lines that need datestr() .

Note: there is an error in your date conversion code . All of the dates come out as being on the second day of the month, but they should be on the first day of the month instead.

Excel had a bug in the design of dates, so that as far as it was concerned February 29, 1900 existed -- it thought 1900 was a leap year, when it is not. You have to make a one day correction because of that. readtable() automatically makes the correction.

[zhize lee]

Thank you very much, can you give me your email, I'll send you the entire code to you.

[Steven Lord]

If later on you do need a text form of the datetime array you can call datestr on it.

d = datetime('now')
s = datestr(d)

[zhize lee]

but, how can just change the code with the original form.Thank you!

[Walter Roberson]

With the posted code, you can just use what I posted already,

t = readtable('data.xlsx');
Time = t{:,1};

You have not posted any code beyond that, and any code beyond that would have to be using datestr() if it wanted datestr because your current code is already generating datetime objects.

can you give me your email

Sorry, I work with code that is posted in public. I do not read most of the code that is sent to me in email; I either let it sit without response, or else I tell the person that they need to post it in public if they want a response from me (unless they want to hire me.)