Import data into datetime format

I'm having trouble importing my data into date time format. My data is in an excel format with tens of thousands of rows.

When I use the import data GUI, the second column is not being read in as a datetime. I was able to combine them in excel, but even the combined date and time were returning NaT. Ultimately I want to plot a combined date and time on the x-axis. I'm using 2021b

Thanks.

Answer 1

[Star Strider]

It would help to have the file and the MATLAB release you are using. It would be better to use readtable if you have it. Also, specify how the ‘Date’ variable is formatted, since it is ambiguous (could be 'dd/MM/yyyy' or 'MM/dd/yyyy') as written.

Assuming the second column is being read in as a duration variable:

T1 = table(datetime('8/1/2018','InputFormat','MM/dd/yyyy'),duration('17:42:56.503'),0.4, 0.3, 'VariableNames',{'Date','Time (GMT)','P','S'})

T1 = 1×4 table
       Date        Time (GMT)     P      S 
    ___________    __________    ___    ___

    01-Aug-2018     17:42:56     0.4    0.3

T1.DateTime = T1.Date + timeofday(datetime(string(T1.('Time (GMT)'))))

T1 = 1×5 table
       Date        Time (GMT)     P      S           DateTime      
    ___________    __________    ___    ___    ____________________

    01-Aug-2018     17:42:56     0.4    0.3    01-Aug-2018 17:42:56

.

Answer 2

[Steven Lord]

Consider opening the file in the Import Tool. Using this tool you can interactively adjust how MATLAB imports each column of your data, including telling it to import the data as a datetime or duration array. You can import a few rows of your data, check that it was imported as you want, and modify the settings if it didn't.

If you have multiple files formatted in the same way you could generate a function (click the downward pointing trianle on the Import Selection button) that uses those settings to read in the data then call that function on the rest of the files. Even if you don't have multiple files to read, generating a script or function file could help you learn the various options available for the data import and export functions.