How to find the first date of each month in a datetime array?
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I have a datetime array as below, and I like to find the first date of each month in the array.
d = [ '14-Jan-2018'
'19-Jan-2018'
'22-Jan-2018'
'26-Jan-2018'
'04-Feb-2018'
'25-Feb-2018'
'09-Apr-2018'
'14-Apr-2018'
'20-Apr-2018'
'10-May-2018'
'21-May-2018'
'01-Jun-2018'
'07-Jun-2018'
'11-Jun-2018'
'11-Jul-2018'
'31-Jul-2018'
'05-Sep-2018'
'07-Sep-2018'
'08-Sep-2018'
'28-Sep-2018'
'29-Sep-2018'
'29-Oct-2018'
'07-Nov-2018'
'12-Nov-2018'
'21-Nov-2018'
'21-Nov-2018'
'03-Dec-2018'
'12-Dec-2018'
'03-Jan-2019'
'04-Jan-2019']
d = datetime(d)
The desired output is as below.
['14-Jan-2018'
'04-Feb-2018'
'09-Apr-2018'
'10-May-2018'
'01-Jun-2018'
'11-Jul-2018'
'05-Sep-2018'
'29-Oct-2018'
'07-Nov-2018'
'03-Dec-2018'
'03-Jan-2019'
]
At first, it seems easy, but only few moments later I realized that it is a way harder and it takes me days on this problem without progress.
Please hlep with this, and thank you so much in advance for any help.
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Accepted Answer
More Answers (1)
Campion Loong
on 30 Aug 2021
Alternatively...
% dateshift all dates to beginning of the month, and find the indices of the first unique entry
[~,idx_first_month_date] = unique(dateshift(d,'start','month'));
% use the indices on your original datetime array
d(idx_first_month_date)
This yields the same result on your input:
ans =
11×1 datetime array
['14-Jan-2018'
'04-Feb-2018'
'09-Apr-2018'
'10-May-2018'
'01-Jun-2018'
'11-Jul-2018'
'05-Sep-2018'
'29-Oct-2018'
'07-Nov-2018'
'03-Dec-2018'
'03-Jan-2019'
]
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