Add date to a time data. Time data is from 7am to 7am.

Hi.

I have an experimental data. The data set is being collected at sampling time of 7am on day one to 7am till next day.

The data is collected in excel. (.xls)

I want to plot the data from 7am Day 1, 12midnight, 7am Day 2 sequence.

When I plot it in matlab, it is being plotted from 00:00 to 24:00.

If I add a date, same date is added to entire data. Including the time after 2400.

desired result.

actual result.

Edit: Data added with the question.

Answer 1

[Star Strider]

It would help to have your Excel file, since I do not know if the time data are a duration array.

Try something like this —

Time = datetime('07:00', 'InputFormat','HH:mm', 'Format','HH:mm') + hours(0:23).';
Data = rand(size(Time));
T1 = table(Time,Data)

T1 = 24×2 table
    Time       Data   
    _____    _________

    07:00      0.03685
    08:00      0.53895
    09:00      0.56889
    10:00      0.45299
    11:00       0.8689
    12:00     0.000849
    13:00       0.6309
    14:00      0.12705
    15:00     0.013077
    16:00      0.70662
    17:00      0.18835
    18:00      0.11612
    19:00    0.0067591
    20:00      0.72767
    21:00       0.4586
    22:00      0.31414

writetable(T1, 'T1_Test.txt');
T1r = readtable('T1_Test.txt');
T1r.Time = datetime(T1r.Time, 'InputFormat','HH:mm')

T1r = 24×2 table
            Time              Data   
    ____________________    _________

    21-Jan-2023 07:00:00      0.03685
    21-Jan-2023 08:00:00      0.53895
    21-Jan-2023 09:00:00      0.56889
    21-Jan-2023 10:00:00      0.45299
    21-Jan-2023 11:00:00       0.8689
    21-Jan-2023 12:00:00     0.000849
    21-Jan-2023 13:00:00       0.6309
    21-Jan-2023 14:00:00      0.12705
    21-Jan-2023 15:00:00     0.013077
    21-Jan-2023 16:00:00      0.70662
    21-Jan-2023 17:00:00      0.18835
    21-Jan-2023 18:00:00      0.11612
    21-Jan-2023 19:00:00    0.0067591
    21-Jan-2023 20:00:00      0.72767
    21-Jan-2023 21:00:00       0.4586
    21-Jan-2023 22:00:00      0.31414

figure
plot(T1r.Time, T1r.Data)
grid
xtickformat('MMM-dd HH:mm')
title('Original')

Date = repmat(datetime('19-Jan-2023'), size(T1,1), 1);                  % Original Date
DI = cumsum([0; diff(hour(Time))<0]);                                   % Day Increment
Date = Date + days(DI);                                                 % Incremented Date
DateTime = Date + timeofday(T1.Time);                                   % Create New VAriable
T1 = addvars(T1,DateTime,'Before','Data');                              % Add It
T1 = removevars(T1,'Time')                                              % Remove 'Time' (Optional)

T1 = 24×2 table
          DateTime            Data   
    ____________________    _________

    19-Jan-2023 07:00:00      0.03685
    19-Jan-2023 08:00:00      0.53895
    19-Jan-2023 09:00:00      0.56889
    19-Jan-2023 10:00:00      0.45299
    19-Jan-2023 11:00:00       0.8689
    19-Jan-2023 12:00:00     0.000849
    19-Jan-2023 13:00:00       0.6309
    19-Jan-2023 14:00:00      0.12705
    19-Jan-2023 15:00:00     0.013077
    19-Jan-2023 16:00:00      0.70662
    19-Jan-2023 17:00:00      0.18835
    19-Jan-2023 18:00:00      0.11612
    19-Jan-2023 19:00:00    0.0067591
    19-Jan-2023 20:00:00      0.72767
    19-Jan-2023 21:00:00       0.4586
    19-Jan-2023 22:00:00      0.31414

figure
plot(T1.DateTime, T1.Data)
grid
xtickformat('MMM-dd HH:mm')
title('Date Crorected')

EDIT — (21 Jan 2023 at 14:42)

Added writetable and readtable to simulate the actual data, and specific comparisons between the original and date-corrected arrays,

.

[Kunal Tiwari]

Undefined function 'hour' for input arguments of type 'cell'.

This is the error I get.

[Star Strider]

I didn’t have the file before.

This runss in R2022b without error —

T1 = readtable('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1272990/Matlab_timedate_example.xls', 'VariableNamingRule','preserve')

T1 = 8946×3 table
    Sr No    data        Time    
    _____    ____    ____________

      0       0      {'07:00:00'}
      1       0      {'07:00:10'}
      2       0      {'07:00:20'}
      3       0      {'07:00:30'}
      4       0      {'07:00:40'}
      5       0      {'07:00:50'}
      6       0      {'07:01:00'}
      7       2      {'07:01:10'}
      8       0      {'07:01:20'}
      9       0      {'07:01:30'}
     10       0      {'07:01:40'}
     11       0      {'07:01:50'}
     12       0      {'07:02:00'}
     13       0      {'07:02:10'}
     14       0      {'07:02:20'}
     15       0      {'07:02:30'}

T1.Time = datetime(T1.Time, 'InputFormat','HH:mm:ss')           % Original

T1 = 8946×3 table
    Sr No    data            Time        
    _____    ____    ____________________

      0       0      24-Jan-2023 07:00:00
      1       0      24-Jan-2023 07:00:10
      2       0      24-Jan-2023 07:00:20
      3       0      24-Jan-2023 07:00:30
      4       0      24-Jan-2023 07:00:40
      5       0      24-Jan-2023 07:00:50
      6       0      24-Jan-2023 07:01:00
      7       2      24-Jan-2023 07:01:10
      8       0      24-Jan-2023 07:01:20
      9       0      24-Jan-2023 07:01:30
     10       0      24-Jan-2023 07:01:40
     11       0      24-Jan-2023 07:01:50
     12       0      24-Jan-2023 07:02:00
     13       0      24-Jan-2023 07:02:10
     14       0      24-Jan-2023 07:02:20
     15       0      24-Jan-2023 07:02:30

figure
plot(T1.Time, T1.data)
grid
VN = T1.Properties.VariableNames;
xlabel('Time')
ylabel('Amplitude')
title('Original')
legend(VN{2})

DI = cumsum([0; diff(hour(T1.Time))<0]);                                % Day Increment
[y,m,d] = ymd(T1.Time);                                                 % Get Year, Month, Day From 'Time'
Date = datetime(y,m,d);                                                 % Create 'Date' From Year, Month, Day
Date = Date + days(DI);                                                 % Incremented Date
DateTime = Date + timeofday(T1.Time);                                   % Create New Variable
T1 = addvars(T1,DateTime,'After','data');                               % Add It
T1 = removevars(T1,'Time')                                              % Remove 'Time' (Optional)

T1 = 8946×3 table
    Sr No    data          DateTime      
    _____    ____    ____________________

      0       0      24-Jan-2023 07:00:00
      1       0      24-Jan-2023 07:00:10
      2       0      24-Jan-2023 07:00:20
      3       0      24-Jan-2023 07:00:30
      4       0      24-Jan-2023 07:00:40
      5       0      24-Jan-2023 07:00:50
      6       0      24-Jan-2023 07:01:00
      7       2      24-Jan-2023 07:01:10
      8       0      24-Jan-2023 07:01:20
      9       0      24-Jan-2023 07:01:30
     10       0      24-Jan-2023 07:01:40
     11       0      24-Jan-2023 07:01:50
     12       0      24-Jan-2023 07:02:00
     13       0      24-Jan-2023 07:02:10
     14       0      24-Jan-2023 07:02:20
     15       0      24-Jan-2023 07:02:30

figure
plot(T1.DateTime, T1.data)
grid
VN = T1.Properties.VariableNames;
xlabel('Time')
ylabel('Amplitude')
title('Date Corrected')
% legend(VN{2})
xtv = linspace(min(T1.DateTime), max(T1.DateTime), 6);
xticks(xtv)
xline(datetime('25-Jan-2023 00:00:00'), '-r', 'Midnight')               % Optional

.

[Kunal Tiwari]

Hi.

I have sucessfull managed to get the data plotted now.

There is another improvement I need to make. I need to collect Time stamp from another file and plot lines to mark specific times in the data.

I tried your midnight line code, I am getting the following error.

Undefined function 'xline' for input arguments of type 'datetime'.

[Star Strider]

The xline function was introduced in R2018b. From the documentation section for the x input, datetime arguments are specifically permitted. It may be worthwhile to upgrade to R2022b (or R2023a, when it is released) if you have an earlier version.

One work-around could be:

plot([0 0]+datetime('25-Jan-2023 00:00:00'), ylim, '-r')
text(datetime('25-Jan-2023 00:00:00'), max(ylim), 'Midnight ', 'Horiz','right', 'Vert','top', 'Rotation',90, 'Color','r')

That will probably work in other versions. (It works in R2022b.)

.