create a sub date time array from a datetime array

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ismail bhamjee 2019-12-16

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https://ww2.mathworks.cn/matlabcentral/answers/496918-create-a-sub-date-time-array-from-a-datetime-array

编辑： Adam Danz 2019-12-18

I have a date time array which has many dates ranging from 1981 till 2017. I would like to create smaller arrays of the years for example and array of 10 years at a time.

my data is kept in one column.

i've tried

>> t=d(1981-01-01):calyears(1):d(1999-12-31)

d being the dates and t being the new array i want to create.

i get and error of

Index in position 2 exceeds array bounds (must not exceed 1)

the first entry in the date time array is 01-12-1981

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dpb 2019-12-16

编辑：dpb 2019-12-17

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Again, why create a new column? What is next after that? Why not just use findgroups and splitapply to process the desired subset(s)? Creating duplicates of data just to do so isn't efficient nor best use of Matlab.

We can't see what would be the benefit from the information so far...

[g gyr]=findgroups(dt.Year);  % find grouping variable by year and years in list

Now splitapply or other logical addressing operations using g and matching will give you all you asked for and more without duplicating the data itself; just pick what is need for a given task.

>> dt=datetime({'01-dec-1981';'03-jan-1983';'23-may-1990';'17-jun-2012'});
>> [g,id]=findgroups(dt.Year)
g =
     1
     2
     3
     4
id =
        1981
        1983
        1990
        2012
>> 

However, what you may be looking for is but not knowing it is the timetable, see <TIMETABLE> and particular the link to the section subscript-into-times-of-timetable>