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Editorial Team
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Asked: 2026-05-27T23:51:09+00:00

In my code I have looped different text files to get the time elapsed

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In my code I have looped different text files to get the time elapsed and the temperature. And then plot temperature and time
The text file has data like this

Date; Time; Temp °C
06.12.2011; 10:35:11;-24.13
06.12.2011; 10:36:34;-24.00
06.12.2011; 10:37:56;-23.88
.
.
.
.

header=fgetl(fid);
data=textscan(fid,'%s','delimiter',';');
fclose(fid);
data=data{:};
day=data(1:3:end);
hour=data(2:3:end);
temp=str2double(data(3:3:end));
time=cellfun(@(x) sprintf('%s %s',day{strcmpi(hour,x)},x),hour,'uniformoutput',0);
timen=datenum(time,'dd.mm.yyyy HH:MM:SS');
seconds=timen*86400/60;
plot(seconds-seconds(1),temp);
xlabel('Time(mins)');
ylabel('Temp °C');

But now when the time elapsed is greater than 24 hrs in the text files(the temperature reading last for more than one day), the datenum gives an error 

Error using ==> dtstr2dtnummx
    Failed on converting date string to date number.

Any suggestions why this is happening, I tried using the same in command line it works fine there

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1 Answer

  1. Editorial Team

    datenum did not fail to me when receiving values for hour greater than 24. For example:

    >> time = '06.12.2011 53:31:11';
>> timen=datenum(time,'dd.mm.yyyy HH:MM:SS');
>> datestr(timen,'dd.mm.yyyy HH:MM:SS')

ans =

08.12.2011 05:31:11

    However, while trying to run your code, I did get the same error but in the cases when there were two observations with the same time stamp. That happens because the line:

    time=cellfun(@(x) sprintf('%s %s',day{strcmpi(hour,x)},x),hour,'uniformoutput',0);

    will concatenate multiple values of day and one value of hour generating an invalid time string such as '07.12.2011 07.12.201110:36:11 '

    Since it looks like you want one value of time per observation (as opposed to one per unique(hour)), I suggest calculating time as 

    time = strcat(day,{' '},hour)
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