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How to use 'setvartype' to get the variable as 'datetime' formatted as: yyyy-MM-dd

Asked by Pawel Jastrzebski on 25 Jul 2018
Latest activity Commented on by Pawel Jastrzebski on 6 Aug 2018
I've got a spreadsheet which gets imported into Matlab via readtable().
Prior to importing I use detectImportOptions() and setvartype() to change the type of certain variables.
Everything works well but one thing, I want the date column of my data to be imported as 'yyyy-MM-dd', but by default I get it gives me 'dd-MM-yyy-hh-mm-ss'.
Problem: I want to ditch the hour-minute-second bit of the date as I don't need it. How to do it via detectImportOptions?
My code:
FileName = 'AllTestData.xlsx';
% detect 'READTABLE' import options for the given sheet
opts = detectImportOptions(FileName);
opts = setvartype(opts,{'Test_Date',},'datetime');
% Import data:
tAllTestData = readtable(FileName,opts);
My current workaround is that, I add this line at the end of code:
tAllTestData.Test_Date = datetime(tAllTestData1.Test_Date,'format', 'yyyy-MM-dd');
But like I said, I'd like to get all the import settings adjusted prior to importing.
To illustrate my problem:

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2 Answers

Answer by Harsh
on 25 Jul 2018
 Accepted Answer

One way is to change the datetime defaults before importing. More on this is here .
For example:
>> datetime.setDefaultFormats('default','yyyy-MM-dd');
>> FileName = 'AllTestData.xlsx';
>> opts = detectImportOptions(FileName);
>> opts = setvartype(opts,{'Test_Date'},'datetime');
>> tAllTestData = readtable(FileName,opts);
>> head(tAllTestData)
ans =
8×2 table
Nr Test_Date
__ __________
1 2017-08-24
2 2017-08-29
3 2017-08-31
4 2017-09-01
5 2017-09-04
6 2017-09-05
7 2017-12-07
8 2017-12-12

  3 Comments

Thank you very much. It works like a charm!
Just to add, alternatively, you could also do the following:
..
>> opts = setvartype(opts,{'Test_Date'},'datetime');
>> opts = setvaropts(opts,{'Test_Date'},'InputFormat','yyyy-MM-dd');
..
Once again thank you. I like the alternative approach better so I'll stick with it. And it's a bit faster base on some tests I've run.

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Answer by Peter Perkins
on 3 Aug 2018

Pawel, if I understand your question correctly, this is just a display issue. The datetime in the middle and right images are the same value, it's just the the right-hand one doesn't display HH:mm:ss. One simple thing to do is set the format after importing:
tallTestData.TestDate.Format = 'dd-MMM-yyyy'
Maybe that's what you've already done, and you wanted to do it as part of the import. But just to be clear: all that is is a display format.

  1 Comment

Peter,
thanks for the suggestion. I've eventually followed Harsh's alternative solution as it made most sense to me to have the date format set prior to importing the data so when it's already imported in Matlab, I don't need to do any additional manipulations.

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