Create a time vector

Hello. I have a problem with my data matrix In fact I have daily data of SST 3D 60*50*14184, respectively longi latitude and sst of which I would like to create a date vector of the type DD/MM/YY of dimensions 14184 only by doing datenum([1979 1 1]):datenum([2017 10 1]) I get a dimension of 14154 yet my data goes exactly from 01/01/1979 to 01/10/2017.Need help please to keep my time vector exactly on schedule. THANK YOU

Answer 1

[Chunru]

 t0 = datenum([1979 1 1 0 0 0])

t0 = 722816

 n = 14184;  % or 14154 
 t = t0 + (0:n-1);
 % Show part of the vector
 datestr(t(end-5:end))

ans = 6×11 char array
    '26-Oct-2017'
    '27-Oct-2017'
    '28-Oct-2017'
    '29-Oct-2017'
    '30-Oct-2017'
    '31-Oct-2017'

Answer 2

[Siddharth Bhutiya]

For dates and time related workflows, you should avoid using legacy functionality like datenum, datestr,etc and use more modern types like datetime. This would make your life a lot easier and avoid the common pitfalls of the older functionality.

Now you mentioned that you get 14154 values, that is because there are 14154 days from Jan 1 1979 to Oct 1 2017, so if you create a vector of dates that increment by 1 day then you should get 14154 values. So as mentioned in the answer above, if you need 14184 values then you need to go to Oct 31 2017.

So if you want to generate a datetime vector from one date to another you can do this as follows

>> dt = datetime([1979 1 1]):datetime([2017 10 31]);
>> size(dt)

ans =

           1       14184

>> dt(end-5:end)

ans = 

  1×6 datetime array

   26-Oct-2017   27-Oct-2017   28-Oct-2017   29-Oct-2017   30-Oct-2017   31-Oct-2017

If you would like to create a datetime vector that starts from a particular date (like Jan 1 1979 in your case) and then increments by one day and goes on for the specified number of days, then you could do something like the following

>> dt = datetime([1979 1 1]) + (0:14183);
>> dt(1:5)

ans = 

  1×5 datetime array

   01-Jan-1979   02-Jan-1979   03-Jan-1979   04-Jan-1979   05-Jan-1979

>> dt(end-5:end)

ans = 

  1×6 datetime array

   26-Oct-2017   27-Oct-2017   28-Oct-2017   29-Oct-2017   30-Oct-2017   31-Oct-2017