I would like to merge two different column in one as datetime

I want to merge these two column in one column as datetime column

[Stephen23]

For what year and month? Is "DAY" to be interpreted as the day of the month, or day of the year, or day since some epoch?

[Younes]

Thanks stephen

I am not using month and year the type of the datetime data that i want like "DD HH:mm"

[Stephen23]

"I am not using month and year the type of the datetime data that i want like "DD HH:mm""

DATETIME objects always have a year and month.

It sould like you should be using a DURATION object instead:

https://www.mathworks.com/help/matlab/ref/duration.html

Answer 1

[Katy Weihrich]

I added two versions. I think you will wanted Version 2 but Version 1 illustrates how to use durations. I prefere to work with durations when no date is given (see Version 1).

%% simulate data
Date = table(ones(9,1),'VariableNames',{'DAY'});
Time = table(char("00:"+string(num2str((0:5:40)','%02.f'))),'VariableNames',{'TIME'});

%% Version 1) transform the number varibale of "Day" into a duration variable
% transform the numeric data into duration
    iday = days(Date.DAY);
% transform the string data into datetime
    itime = datetime(string(Time.TIME),"InputFormat","hh:mm");
    % transform the datetime data into duration
    imin = minutes(minute(itime));
    ih = hours(hour(itime));
% add day + h + min durations together
iduration = iday+ih+imin;

% Output: 
        %  iduration = 
        %   9×1 duration array
        %          1 day
        %    1.0035 days
        %    1.0069 days
        %    1.0104 days
        %    1.0139 days
        %    1.0174 days
        %    1.0208 days
        %    1.0243 days
        %    1.0278 days

%% Version 2: transform the char data into datetime, remove today and add the day as duration
% note: if no day is given, datetime gives you the current day and time
        % >> datetime
        % ans = 
        %   datetime
        %    29-Aug-2023 15:29:24
        
        % >> datetime(string(Time.TIME(5,:)),"InputFormat","hh:mm")
        % ans = 
        %   datetime
        %    29-Aug-2023 00:20:00

itime = datetime(string(Time.TIME),"InputFormat","hh:mm") - today('datetime') + days(Date.DAY);
% Output: 
        % itime = 
        %   9×1 duration array
        %    24:00:00
        %    24:05:00
        %    24:10:00
        %    24:15:00
        %    24:20:00
        %    24:25:00
        %    24:30:00
        %    24:35:00
        %    24:40:00

[Katy Weihrich]

if you want it as datetime formated like this: "DD HH:mm" use:

itime = datetime(string(Time.TIME),"InputFormat","hh:mm") - today('datetime') + days(Date.DAY);
itime = datetime(datenum(itime),'ConvertFrom','datenum','Format',"dd HH:mm")

[Stephen23]

"if you want it as datetime formated like this: "DD HH:mm" use: "

No, do NOT convert to serial date number with its assocated loss of precision. Avoid deprecated DATENUM etc.

Simply adjust the FORMAT of the DATETIME object e.g.:

DT= datetime('now')

DT = datetime
   31-Aug-2023 04:32:21

DT.Format = 'dd HH:mm' % simpler, no loss of precision, more efficient

DT = datetime
   31 04:32

[Katy Weihrich]

Thank you. I keep forgetting that you can change datetimes properties this way.

[Younes]

Thank you very much for your help

Answer 2

[Stephen23]

% Fake data:
A = ones(5,1)

A = 5×1

1 1 1 1 1

B = {'0:00';'0:05';'0:10';'0:15';'0:20'}

B = 5×1 cell array
    {'0:00'}
    {'0:05'}
    {'0:10'}
    {'0:15'}
    {'0:20'}

% Convert to DURATION:
M = str2double(split(B,':'));
D = days(A)+duration(M(:,1),M(:,2),0);
D.Format = 'dd:hh:mm:ss'

D = 5×1 duration array
   01:00:00:00
   01:00:05:00
   01:00:10:00
   01:00:15:00
   01:00:20:00

[Younes]

it's very helpful