Using System.DateTime in a Timetable

Hello everyone,

i am importing Data from a Database and want to save the timestamps and the values in a timetable. However the Time gets imported as System.DateTime, which I cannot use in a timetable, at least I get an error, when I try.

The System.DateTime 'netTime' looks like this:

K>> netTime(1)

ans = 

  DateTime with properties:

           Date: [1×1 System.DateTime]
            Day: 29
      DayOfWeek: Thursday
      DayOfYear: 119
           Hour: 6
           Kind: Unspecified
    Millisecond: 300
         Minute: 0
          Month: 4
            Now: [1×1 System.DateTime]
         UtcNow: [1×1 System.DateTime]
         Second: 0
          Ticks: 637552728003000000
      TimeOfDay: [1×1 System.TimeSpan]
          Today: [1×1 System.DateTime]
           Year: 2021
       MinValue: [1×1 System.DateTime]
       MaxValue: [1×1 System.DateTime]

What i Want is to only the Time hh:mm:ss:ms from this "cell" to use in a TT.

Can anyone tell me what I need to do?

Thanks in advance

Answer 1

[Scott MacKenzie]

This converts the System.DateTime variable returned by netTime to a datetime variable, which can then be used with timetable:

t = netTime(1); % t is System.DateTime variable

% convert to datetime variable
t2 = datetime(t.Year, t.Month, t.Day, t.Hour, t.Minute, t.Second, t.Millisecond)

[Sebastian Ehrismann]

Unfortunately, when I try:

netTime.Year

I get

No appropriate method, property, or field

'Year' for class 'System.DateTime[]'.

as an Error Message.

netTime(1).Year

Gives me the year of the first Data point.

I should also mention that netTime has a size of 325670.

is there anything else i can try?

[Scott MacKenzie]

There's a big difference between netTime and netTime(1). netTime(1) is just one System.DateTime element. And, yes, netTime(1).Year gives the year value for the SystemDateTime elment in position 1 of netTime. BTW, netTime(1).Year (your code) is the same as t.Year (my code). Did you try the code in my answer? I'm still thinking it should work

[Sebastian Ehrismann]

I am sorry, I misread your answer and you are correct. Your suggested code works.

However, the datetime won't show the Milliseconds. I tried to add

datetime(t.Year, t.Month, t.Day, t.Hour, t.Minute, t.Second, t.Millisecond, 'InputFormat', 'yyyy-mm-dd HH:MM:SS.SSS');

but i will still not consider the Millisenconds. In this case they are needed for calculations.

Any ideas how to involve them?

[Walter Roberson]

InputFormat is only used when parsing a character vector or string object. You should be using Format to control what is displayed.

[Sebastian Ehrismann]

Thank you Scott and Walter, the Code is now running without problems.

Since it is now working, I have a question concerning the performance. Although Scott's code is working, it is quite slow, are there any possibilities to increase speed?

[Scott MacKenzie]

You're welcome.

Obviously, issues with execution time relate to retrieving data from the database. I really don't have any insights to offer on this. Sorry.

[Steven Lord]

Profile the code (possibly on a small sample of your data) to identify the bottlenecks. Depending on what the code in the bottlenecks is doing it may be possible to speed them up, but it could be difficult if not impossible to offer specific guidance without seeing the actual code you're executing.