time date to datenum and datenum to datetime

Question

Ismita 2022-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/1705415-time-date-to-datenum-and-datenum-to-datetime

回答： Corey Silva 2022-5-18

I have time in 'yyyy-MM-dd''T''HH:mm:ss.SSS''Z' formate (e.g., [2018-08-01T20:05:00.000Z; 2018-08-01T20:10:00.000Z; 2018-08-01T20:35:00.000Z; 2018-08-01T25:05:00.000Z] . How to make time string and datetime to datenum and datenum to datetime?

Thanks in advance.

(I am new in matlab.)

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Stephen23 2022-4-26

编辑：Stephen23 2022-4-26

"But I need it serially here"

What is the exact operation that requires a serial date number?

Both DATETIME and DURATION objects support many many methods and functions, if you actually explained how you are going to process your data then we could help you use a better approach.

Ismita 2022-4-26

Thank you. You can check the data attached in the comment threading.

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Answer 1

Bruno Luong 2022-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/1705415-time-date-to-datenum-and-datenum-to-datetime#answer_951280

编辑：Bruno Luong 2022-4-26

在 MATLAB Online 中打开

I make a round conversion so you can convert any format to any other by using the appropriate substeps

dt=datetime(2022,04,28,13,09,00,'Format','yyyy-MM-dd''T''HH:mm:ss.SSS''Z''')
dt = datetime
   2022-04-28T13:09:00.000Z
dn=datenum(dt)
dn = 7.3864e+05
ds = datestr(dn)
ds = '28-Apr-2022 13:09:00'
dt = datetime(ds,'InputFormat','dd-MMM-yyyy HH:mm:SS','Format','yyyy-MM-dd''T''HH:mm:ss.SSS''Z''')
dt = datetime
   2022-04-28T13:09:00.000Z

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Bruno Luong 2022-4-26

编辑：Bruno Luong 2022-4-26

在 MATLAB Online 中打开

File.txt

Thanks goodness finally a data file.

Import and convert to datetime as below, do the rest as with my earlier answer

s=readtable('File.txt')
s = 10×10 table
                Var1                Var2     Var3     Var4      Var5     Var6    Var7     Var8    Var9     Var10
    ____________________________    _____    _____    _____    ______    ____    _____    ____    _____    _____

    {'2008-01-01T00:00:00.000Z'}    -1.06      4.3      1.2    -355.9      -9    -16.6    6.58    66335       0 
    {'2008-01-01T00:05:00.000Z'}       -1     3.89     1.26    -353.4    -6.7      -18     6.6    71037     300 
    {'2008-01-01T00:10:00.000Z'}    -1.76     3.22     -0.7      -350     0.6    -11.9    6.59    74186     600 
    {'2008-01-01T00:15:00.000Z'}    -2.09     3.29    -0.49    -349.5      -2     -4.4    6.62    88787     900 
    {'2008-01-01T00:20:00.000Z'}    -1.74      2.3    -1.49    -351.4    -2.6     -3.7    6.65    82061    1200 
    {'2008-01-01T00:25:00.000Z'}    -3.27     0.41    -2.61    -346.2     2.8     -0.3    6.47    74540    1500 
    {'2008-01-01T00:30:00.000Z'}    -3.64    -0.44    -2.43    -343.7     8.4      3.5    6.09    82033    1800 
    {'2008-01-01T00:35:00.000Z'}    -3.65     0.27    -1.81    -343.2    12.4        0    6.35    82179    2100 
    {'2008-01-01T00:40:00.000Z'}     -3.4     1.72    -1.67    -341.8     5.7      5.2    6.15    77514    2400 
    {'2008-01-01T00:45:00.000Z'}    -3.68     0.59    -1.39    -343.1     0.5     -4.7    6.27    80708    2700 
ts=table2cell(s(:,1))
ts = 10×1 cell array
    {'2008-01-01T00:00:00.000Z'}
    {'2008-01-01T00:05:00.000Z'}
    {'2008-01-01T00:10:00.000Z'}
    {'2008-01-01T00:15:00.000Z'}
    {'2008-01-01T00:20:00.000Z'}
    {'2008-01-01T00:25:00.000Z'}
    {'2008-01-01T00:30:00.000Z'}
    {'2008-01-01T00:35:00.000Z'}
    {'2008-01-01T00:40:00.000Z'}
    {'2008-01-01T00:45:00.000Z'}
dtformat = 'yyyy-MM-dd''T''HH:mm:ss.SSS''Z';
dt = datetime(ts,'Format',dtformat,'InputFormat',dtformat)
dt = 10×1 datetime array
   2008-01-01T00:00:00.000Z
   2008-01-01T00:05:00.000Z
   2008-01-01T00:10:00.000Z
   2008-01-01T00:15:00.000Z
   2008-01-01T00:20:00.000Z
   2008-01-01T00:25:00.000Z
   2008-01-01T00:30:00.000Z
   2008-01-01T00:35:00.000Z
   2008-01-01T00:40:00.000Z
   2008-01-01T00:45:00.000Z

Bruno Luong 2022-4-26

编辑：Bruno Luong 2022-4-26

在 MATLAB Online 中打开

They are table, if you aceess them by column name, it returns the standard column-vector of doubles

s.Var2 + s.Var3

Ismita 2022-4-26

thanks a lot.

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Answer 2

Steven Lord 2022-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/1705415-time-date-to-datenum-and-datenum-to-datetime#answer_951530

在 MATLAB Online 中打开

I'm going to assume that you've imported this data into MATLAB as a string array or a cellstr with two columns. Since I don't have the file or whatever other source this data comes from, I'll hard code it so my example can operate on it.

S = ["2008-01-01T00:00:00.000Z",	"-1.06";
     "2008-01-01T00:05:00.000Z",	"-1";	
     "2008-01-01T00:10:00.000Z",	"-1.76";	
     "2008-01-01T00:15:00.000Z",	"-2.09"];

Let's create a datetime array using the first column of S.

fmt = 'yyyy-MM-dd''T''HH:mm:ss.SSS''Z''';
dt = datetime(S(:, 1), 'InputFormat', fmt, 'Format', fmt)
dt = 4×1 datetime array
   2008-01-01T00:00:00.000Z
   2008-01-01T00:05:00.000Z
   2008-01-01T00:10:00.000Z
   2008-01-01T00:15:00.000Z

Now to create a double array using the second column of S.

n = double(S(:, 2))
n = 4×1
   -1.0600
   -1.0000
   -1.7600
   -2.0900

Finally, storing this date and time data along with the numeric data in a timetable array would let us perform future operations on the data easily.

T = timetable(dt, n)
T = 4×1 timetable
               dt                 n  
    ________________________    _____

    2008-01-01T00:00:00.000Z    -1.06
    2008-01-01T00:05:00.000Z       -1
    2008-01-01T00:10:00.000Z    -1.76
    2008-01-01T00:15:00.000Z    -2.09

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Ismita 2022-4-26

编辑：Ismita 2022-4-26

Thank you so much. Could you please inform me the type of 'T=timetable(dt,n)' data is text/numeric?

Should I use 'double(n)' / 'table2array(n)' for other variables like 'n' here?

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Answer 3

Corey Silva 2022-5-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1705415-time-date-to-datenum-and-datenum-to-datetime#answer_966570

While serial date numbers (datenum) can represent dates and times, it is recommended that you use datetime values to represent points in time, and durationor calendarDuration values to represent elapsed times.