Combining Date and Time variables (class - datetime) into 1 DateTime (class - double) array

I import my data with:

Date = dataArray{:, 6}; Time = dataArray{:, 7};

Date as a 'datetime' value with format: 'dd.mm.yyyy' and

Time as a 'datetime' value with format: 'HH:MM'.

I can convert both of these using datenum:

Date2=datenum(Date); Time2=datenum(Time);

How do I now combine Date2 and Time2 to make one DateTime array?

Example: Date= 06.07.2010

      06.07.2010

Time= 22:31

      22:41

Date2 = 7.341440048611110e+05

        7.341440048611110e+05

Time2 = 7.359039381944444e+05

        7.359039451388889e+05

I tried including a format specification in the datenum code line but kept on getting an error (Erro using Datetime/datenum - Too many input arguments)

Date2 = datenum(Date, 'dd.mm.yyyy');

Time2 = datenum(Time, 'HH:MM');

I would like to generate one DateTime array that would look as follows as a string:

06.07.2010 22:31

06.07.2010 22:41

Thanks in advance, Jenny

Answer 1

[Star Strider]

I haven’t used the new datetime functions much, and I don’t have your array. This works on the example you gave:

Date = datetime('06.07.2010','InputFormat','dd.MM.yyyy');
Time = datetime('22:31','InputFormat','HH:mm');
CnvtDT = @(Date,Time) datetime([Date.Year  Date.Month  Date.Day  Time.Hour  Time.Minute 0], 'Format', 'dd.MM.yyyy HH:mm');
DateTime2 = CnvtDT(Date,Time)          % Check Output

The output is also a ‘datetime’ structure.

[Jenny]

Thank you for that answer. It does work on the one point but when I try to convert the entire array, I receive an error message that the dimension of the matrices being concatenated are not consistent.

My data is as follows:

Date - 4033 x 1 datetime array (format dd.mm.yyyy)

Time - 4033 x 1 datetime array (format hh:mm)

How do I adjust your CnvtDT to convert the entire array and not just one point?

Thank you in advance Jenny

[Star Strider]

My pleasure!

Please attach a sample of your date and time datetime vectors that are causing the error and I’ll see if I can fix the problem. I’d like to be able to vectorise it and avoid a loop, but we’ll get it running regardless.

The datetime functions are useful, but unless you need your dates and time as datetime objects, it might be easier to go with date numbers or date vectors.

[Jenny]

Hi.

I have attached the data file that I am working with.

The date and time are used really only for plotting but the first date / time is also the start point of an analysis on the data so it needs to be correct.

I would greatly appreciate any help on combining the date and time into one array.

Jenny

[Star Strider]

This works:

fidi = fopen('sandholmen5m0810.txt');
D = textscan(fidi, '%f%f%f%f%f%s%s','Delimiter',';', 'Headerlines',2);
fclose(fidi);
dates = [char(D{6}) char(D{7})];            % Isolate Date Time As ‘char’
daten = datenum(dates, 'dd.mm.yyyyHH:MM');  % Convert To Date Numbers
datev = datevec(daten);                     % Convert To Date Vectors
dds = dates(1:5,:);             % Check: Original Data
ddv = datev(1:5,:);             % Check: Correct Conversion

It reads the entire file, then creates date and time strings out of the date and time cells (here D{6} and D{7}), converts them to date numbers in the ‘daten’ variable, then converts that to date vectors in the ‘datev’ variable. I read everything in as floating-point values except the date and time.

The ‘dds’ variable displays a sample of the original data, and ‘ddv’ the date vectors of those same data. Both ‘dds’ and ‘ddv’ can be deleted, since they are only to be sure that the conversion was correct.

[Star Strider]

Jenny — What problems do you have with the code I provided? It reads in everything and converts the dates to date numbers. After that you can convert the date numbers to datetime objects with:

DateTime = datetime(daten, 'ConvertFrom', 'datenum');

Everything else is provided as individual cell vectors in D{1:5}.

[Jenny]

Thank you

Jenny

[Star Strider]

My pleasure!

Answer 2

[Peter Perkins]

Jenny, if you create datetimes from strings and don't specify the time portion, it defaults to midnight. If you don't specify the date portion, it defaults to "today". So

>> Date = datetime('06.07.2010','InputFormat','dd.MM.yyyy')
Date = 
   06-Jul-2010
>> Time = datetime('22:31','InputFormat','HH:mm')
Time = 
   25-Nov-2014 22:31:00

Then all you need to do is extract the time of day from the second array

>> timeofday(Time)
ans = 
   22:31:00

and add that to the first array:

>> DateAndTime = Date + timeofday(Time)
DateAndTime = 
   06-Jul-2010 22:31:00

Hope this helps.

[Jenny]

Hi Peter.

I have not managed to get this to work for me in the way that you describe.

The format for the Date and the Time are specified in the formatSpec.

I am not sure what I am doing wrong here:

With the data set that I attached above and the code below, for the DateAndTime, I get the result

06.38.2010

06.48.2010

06.58.2010

06.08.2010 ...

Thanks - Jenny

filename = 'sandholmen5m0810.txt';
delimiter = ';'
startRow = 3;

%%Format string for each line of text:
formatSpec = '%f%f%f%f%f%{dd.mm.yyyy}D%{HH:mm}D%*s%[^\n\r]';

%%Open the text file.
fileID = fopen(filename,'r');

%%Read columns of data according to format string.
dataArray = textscan(fileID, formatSpec, 'Delimiter', delimiter, 'EmptyValue' ,NaN,'HeaderLines' ,startRow-1, 'ReturnOnError', false);

%%Close the text file.
fclose(fileID);

%%Allocate imported array to column variable names
Ser = dataArray{:, 1};
Meas = dataArray{:, 2};
Temp = dataArray{:, 3};
Curr = dataArray{:, 4};
Dir = dataArray{:, 5};
Date = dataArray{:, 6};
Time = dataArray{:, 7};

%%Combine Date and Time
DateAndTime=Date+timeofday(Time);

[Peter Perkins]

Two things:

1) You've used 'mm' where you want 'MM': the format to textscan should be %{dd.MM.yyyy}D. I don't have your file, but I assume that's why you get 38, 48, etc.

2) All you need to do is to set the format. Your Date and Time variables have the formats from your call to textscan, and Date+timeofday(Time) preserves the format of Date. So set the format of the result to whatever you want. Perhaps like this

DateAndTime.Format = [Date.Format ' ' Time.Format]