How can I do a datetime vector?

Hello, how can I do a datime vector. I have a vector whose name is T where I have date and time in this format : '03/19/2019 16:36:41', I want only the time so I write:

for(i=2:n)%I don't want the first row so I start from 2
    a=T{i}; 
    x(i,:)=a(11:end);
 ...

then I want to put every element of x (x is a matrix 1159x9) into a datetime vector so I do:

     for (j=1:n-1)
        H{j}=datetime(x(i,:),'Format','HH:mm:ss');
     end
end

Matlab doesn't show any error but if I try to view H{34}, for example, it doesn't show me anything.

[dpb]

>> t= '03/19/2019 16:36:41';      % your sample input form...
>> datetime(t(11:end))
ans = 
  datetime
   25-Mar-2019 16:36:41
>>

shows that with datetime you simply cannot have just a time; there's always an implied date if not a specific one.

You can return arrays of the time components from a datetime array but you can't create the array in the beginning without a date being associated with the time. I, personally, tend to think this is an undesireable limitation as well, but it is what it is and I don't see TMW changing it.

Time-only vectors can only be some form of a duration; either calendar or absolute.

Your code not returning anything is an error don't see a cause for otomh, but you don't need a loop as datetime is vectorized for cell array of strings but you can't actually do what you're trying to do anyways...

Answer 1

[Star Strider]

Just do something like this:

T = datetime('03/19/2019 16:36:41')
H = datetime(T,'Format','HH:mm:ss')

producing:

T = 
  datetime
   19-Mar-2019 16:36:41

H = 
  datetime
   16:36:41

[dpb]

NB to OP: H still has the date associated with it, you simply can't get away from that, H is just formatted to only display the time portion.

>> T = datetime('03/19/2019 16:36:41');
H = datetime(T,'Format','HH:mm:ss');
>> T==H
ans =
  logical
   1
>> 

As you see, they're both the same datetime value; just displayed as per the format property.

Whether this matters at all only depends on the use intended which we don't know...

[Star Strider]

True for datetime arrays.

If you only want the time as a (1x8) character vector, do this:

H = datestr(T, 'hh:mm:ss')

producing:

H =
    '16:03:41'

[dpb]

Yeah, I still don't understand TMW's thinking on forcing the date to exist instead of just letting one have an array of times if that's all one wants for a given task.

With the venerable datenum since it's just a double(), one can do so easily by throwing away the integer portion but it has all the other issues associated with it so it's not all that attractive of a solution, either.