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How can I convert datetime into double?

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bluebar
bluebar il 11 Dic 2019
Risposto: Tianchu Lu il 16 Giu 2024 alle 15:25
I have a data which is 60 x 4320 datetime, each cell is 2019/01/01 00:00:00 and want to convert this into 60 x 4320 double.
I tried to use datevec(data) but it resulted 259200 x 6 double, one row one character, like
2019 01 01 00 00 00
2019 01 01 00 10 00
2019 01 01 00 20 00
  3 Commenti
MatLab Code N
MatLab Code N il 17 Nov 2021
it is not possible to merge datetime with other double variables
Steven Lord
Steven Lord il 17 Nov 2021
You cannot have a double array where some of the elements are datetime values, that is true. But if you have date- and/or time-stamped data, I suggest using a timetable instead.
T = datetime('today');
randomDays = T + days(randi([-7 7], 10, 1));
x = (1:10).';
myTimedData = timetable(randomDays, x)
myTimedData = 10×1 timetable
randomDays x ___________ __ 15-Nov-2021 1 11-Nov-2021 2 16-Nov-2021 3 18-Nov-2021 4 13-Nov-2021 5 11-Nov-2021 6 22-Nov-2021 7 13-Nov-2021 8 15-Nov-2021 9 11-Nov-2021 10

Accedi per commentare.

Risposte (3)

galaxy
galaxy il 12 Dic 2019
You can use datenum to convert each your data to double.
Example:
>> t = datetime('now')
t =
datetime
2019/12/12 09:43:30
>> DateNumber = datenum(t)
DateNumber =
7.3777e+05
After that, if you want to convert back:
>> datetime(DateNumber,'ConvertFrom','datenum')
ans =
datetime
2019/12/12 09:43:30
hope it helps

Eric Sofen
Eric Sofen il 13 Dic 2019
What do you want the doubles to represent?
Datenum returns a double represents days since 0 CE.
The posixtime function would give you a double representing seconds since the Unix epoch (00:00:00 1-Jan-1970 UTC).
The juliandate function gives a double representing days since...
The trouble with using double to represent dates and times is that there isn't one definition (there are also precision-related issues over long spans of time).
I'm curious if you'd be willing to share what you want to do with the doubles, and why you can't do it using datetime?

Tianchu Lu
Tianchu Lu il 16 Giu 2024 alle 15:25
Hi,
I have got the same problem, and I think I have managed to solve it.
This function does exactly what it is. Although this is for a cell array, just change {} brace bracket to () round bracket if your data type is not a cell type.
But please let me know if you are going to use it.
Thanks
Tian
function datetime_double_matrix = convertDatetimeCellArray(datetime_array)
% Convert a 1xN cell array of datetime strings to a 6xN double matrix
% in the order of [YYYY, MM, DD, HH, MN, SS]
% Initialize a matrix to store the date vectors
num_entries = length(datetime_array);
datetime_double_matrix = zeros(6, num_entries);
% Loop through the cell array and convert each datetime to a date vector
for i = 1:num_entries
% Convert the datetime string to a date vector
date_vector = datevec(datetime_array{i});
% Transpose the date vector and store it in the matrix
datetime_double_matrix(:, i) = date_vector';
end
end

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