Extend a cell array of dates (from days only, to hours and days) in a compact way

I have a cell vector containing 44 dates, i.e. days:

>> C

ans =

  44×1 cell array

    {'17-Jun-2017'}
    {'18-Jun-2017'}
    {'19-Jun-2017'}
    ...
    {'28-Jul-2017'}
    {'29-Jul-2017'}
    {'30-Jul-2017'}

I would like to "extend" that cell vector to include the 24 hours as well, in each day.

This means that my cell vector will pass from 44 elements (i.e. the 44 days) to 24 * 44 = 1056 elements (i.e. 24 hours in each day). Something like this:

% Desired Output (something like this)
>> D

ans =

  1056×1 cell array

    {'17-Jun-2017 00:00:00'}
    {'17-Jun-2017 01:00:00'}
    {'17-Jun-2017 02:00:00'}
    ...
    {'17-Jun-2017 23:00:00'}
    {'18-Jun-2017 00:00:00'}
    {'18-Jun-2017 01:00:00'}
    {'18-Jun-2017 02:00:00'}
    ...
    {'29-Jul-2017 23:00:00'}   
    {'30-Jul-2017 00:00:00'}

Any idea on how to do it in a compact way ?

Maybe there is a simple in-built function in Matlab to do that, and that I am probably missing right now..

Answer 1

[Star Strider]

Try this —

C1 = {'17-Jun-2017'; '30-Jul-2017'}

C1 = 2×1 cell array
    {'17-Jun-2017'}
    {'30-Jul-2017'}

DT1 = [datetime(C1{1}) : days(1) : datetime(C1{end})]'

DT1 = 44×1 datetime array
   17-Jun-2017
   18-Jun-2017
   19-Jun-2017
   20-Jun-2017
   21-Jun-2017
   22-Jun-2017
   23-Jun-2017
   24-Jun-2017
   25-Jun-2017
   26-Jun-2017
   27-Jun-2017
   28-Jun-2017
   29-Jun-2017
   30-Jun-2017
   01-Jul-2017
   02-Jul-2017
   03-Jul-2017
   04-Jul-2017
   05-Jul-2017
   06-Jul-2017
   07-Jul-2017
   08-Jul-2017
   09-Jul-2017
   10-Jul-2017
   11-Jul-2017
   12-Jul-2017
   13-Jul-2017
   14-Jul-2017
   15-Jul-2017
   16-Jul-2017

DT2 = [min(DT1): hours(1) : max(DT1)]'

DT2 = 1033×1 datetime array
   17-Jun-2017 00:00:00
   17-Jun-2017 01:00:00
   17-Jun-2017 02:00:00
   17-Jun-2017 03:00:00
   17-Jun-2017 04:00:00
   17-Jun-2017 05:00:00
   17-Jun-2017 06:00:00
   17-Jun-2017 07:00:00
   17-Jun-2017 08:00:00
   17-Jun-2017 09:00:00
   17-Jun-2017 10:00:00
   17-Jun-2017 11:00:00
   17-Jun-2017 12:00:00
   17-Jun-2017 13:00:00
   17-Jun-2017 14:00:00
   17-Jun-2017 15:00:00
   17-Jun-2017 16:00:00
   17-Jun-2017 17:00:00
   17-Jun-2017 18:00:00
   17-Jun-2017 19:00:00
   17-Jun-2017 20:00:00
   17-Jun-2017 21:00:00
   17-Jun-2017 22:00:00
   17-Jun-2017 23:00:00
   18-Jun-2017 00:00:00
   18-Jun-2017 01:00:00
   18-Jun-2017 02:00:00
   18-Jun-2017 03:00:00
   18-Jun-2017 04:00:00
   18-Jun-2017 05:00:00

C2 = compose('%s',string(DT2))

C2 = 1033×1 cell array
    {'17-Jun-2017 00:00:00'}
    {'17-Jun-2017 01:00:00'}
    {'17-Jun-2017 02:00:00'}
    {'17-Jun-2017 03:00:00'}
    {'17-Jun-2017 04:00:00'}
    {'17-Jun-2017 05:00:00'}
    {'17-Jun-2017 06:00:00'}
    {'17-Jun-2017 07:00:00'}
    {'17-Jun-2017 08:00:00'}
    {'17-Jun-2017 09:00:00'}
    {'17-Jun-2017 10:00:00'}
    {'17-Jun-2017 11:00:00'}
    {'17-Jun-2017 12:00:00'}
    {'17-Jun-2017 13:00:00'}
    {'17-Jun-2017 14:00:00'}
    {'17-Jun-2017 15:00:00'}
    {'17-Jun-2017 16:00:00'}
    {'17-Jun-2017 17:00:00'}
    {'17-Jun-2017 18:00:00'}
    {'17-Jun-2017 19:00:00'}
    {'17-Jun-2017 20:00:00'}
    {'17-Jun-2017 21:00:00'}
    {'17-Jun-2017 22:00:00'}
    {'17-Jun-2017 23:00:00'}
    {'18-Jun-2017 00:00:00'}
    {'18-Jun-2017 01:00:00'}
    {'18-Jun-2017 02:00:00'}
    {'18-Jun-2017 03:00:00'}
    {'18-Jun-2017 04:00:00'}
    {'18-Jun-2017 05:00:00'}

It simply creates a new datetime vector with a different increment from the original cell array, and then uses the compose function to create a new cell array from that. (I would keep it as a datetime array rather than converting it back to a cell array.)

.

[Sim]

cool! Exactly what I was thinking ! Many thanks!

[Star Strider]

As always, my pleasure!

[Sim]

.......wait a sec..... both DT2 and C2 should have 1056 elements and not 1033...... what is missing ? :-)

@Star Strider do you know why ?

[Sim]

In addition, in my machine

>> version

ans =

    '9.7.0.1216025 (R2019b) Update 1'

I do not get the hours.....strange....

>> datetime('today'):hours(8):datetime('tomorrow')

ans = 

  1×4 datetime array

   17-May-2022   17-May-2022   17-May-2022   18-May-2022

   

@Star Strider do you know why?

[Star Strider]

@Sim —

With respect to your first Comment, I am just going on the available data.

With respect to your second Comment, use the Format property.

.

[Sim]

@Star Strider Thanks a lot, very kind!! :-)

[Star Strider]

As always, my pleasure!

Answer 2

[Mitch Lautigar]

Use for loops. Here's an untested example of what I mean.

stack_array = [];

for i = 1:length(C)

curr_date = C(i);

for j = 1:24

stack_array = [stack_array;cell(strjoin(cellstr(curr_date),'-',num2str(j)) )];

end

end

In theory, this code would loop through and for every date in your C loop, add in the hours with a dash in the middle to keep the formatting you have above. Hope it helps!

[Sim]

Thanks a lot @Mitch Lautigar! But, unfortunately, it does not work...

Error using strjoin
Too many input arguments.
 
Error using strjoin
Too many input arguments.

Error in untitled3 (line 5)
        stack_array = [stack_array;cell(strjoin(cellstr(curr_date),'-',num2str(j)) )];

[Sim]

this works for me:

D = [];
k = 1;
for i = 1:length(C)
    for j = 0:23
        D{k} = strjoin([C(i),sprintf('%d:00:00',j)]);
        k = k + 1;
    end
end

which gives:

>> D

  Columns 1053 through 1055

    {'30-Jul-2017 20:00:00'}    {'30-Jul-2017 21:00:00'}    {'30-Jul-2017 22:00:00'}

  Column 1056

    {'30-Jul-2017 23:00:00'}
    

But I was thinking if there is a more compact way.... I mean not using the loop for....

Answer 3

[Mitch Lautigar]

stack_array = [stack_array;cell(strjoin(cellstr(curr_date),'-',num2str(j)) )]; should be:

stack_array = [stack_array; cell(strjoin(cellstr(curr_date),'-',num2str(j),'') )]; forgot to tell strjoin how to join the command.

[Sim]

thanks a lot @Mitch Lautigar for the amendment, very kind!

Answer 4

[Steven Lord]

I'd probably take advantage of implicit expansion for datetime and duration arrays, introduced for those types in release R2020b.

C = {'17-Jun-2017'; '18-Jun-2017'; '19-Jun-2017'}

C = 3×1 cell array
    {'17-Jun-2017'}
    {'18-Jun-2017'}
    {'19-Jun-2017'}

theDays = datetime(C).'

theDays = 1×3 datetime array
   17-Jun-2017   18-Jun-2017   19-Jun-2017

theHours = hours(0:23).'

theHours = 24×1 duration array
    0 hr
    1 hr
    2 hr
    3 hr
    4 hr
    5 hr
    6 hr
    7 hr
    8 hr
    9 hr
   10 hr
   11 hr
   12 hr
   13 hr
   14 hr
   15 hr
   16 hr
   17 hr
   18 hr
   19 hr
   20 hr
   21 hr
   22 hr
   23 hr

D = theDays + theHours; % Adding a row vector and a column vector gives a matrix
D = reshape(D, [], 1)

D = 72×1 datetime array
   17-Jun-2017 00:00:00
   17-Jun-2017 01:00:00
   17-Jun-2017 02:00:00
   17-Jun-2017 03:00:00
   17-Jun-2017 04:00:00
   17-Jun-2017 05:00:00
   17-Jun-2017 06:00:00
   17-Jun-2017 07:00:00
   17-Jun-2017 08:00:00
   17-Jun-2017 09:00:00
   17-Jun-2017 10:00:00
   17-Jun-2017 11:00:00
   17-Jun-2017 12:00:00
   17-Jun-2017 13:00:00
   17-Jun-2017 14:00:00
   17-Jun-2017 15:00:00
   17-Jun-2017 16:00:00
   17-Jun-2017 17:00:00
   17-Jun-2017 18:00:00
   17-Jun-2017 19:00:00
   17-Jun-2017 20:00:00
   17-Jun-2017 21:00:00
   17-Jun-2017 22:00:00
   17-Jun-2017 23:00:00
   18-Jun-2017 00:00:00
   18-Jun-2017 01:00:00
   18-Jun-2017 02:00:00
   18-Jun-2017 03:00:00
   18-Jun-2017 04:00:00
   18-Jun-2017 05:00:00

[Sim]

Oh great @Steven Lord !!

Amazing, thanks a lot! :-)