How to find (i) unique datetimes and (ii) count their occurences?

Question

Sim 2023-6-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982764-how-to-find-i-unique-datetimes-and-ii-count-their-occurences

回答： Sim 2023-6-14

% Input
a = [{'22-Jun-2023 09:00:00'}
    {'23-Jun-2023 19:00:00'}
    {'24-Jun-2023 16:00:00'}
    {'24-Jun-2023 11:00:00'}
    {'19-Jun-2023 16:00:00'}
    {'20-Jun-2023 10:00:00'}
    {'21-Jun-2023 10:00:00'}
    {'22-Jun-2023 09:00:00'}
    {'23-Jun-2023 14:00:00'}
    {'19-Jun-2023 17:00:00'}
    {'20-Jun-2023 11:00:00'}
    {'21-Jun-2023 17:00:00'}
    {'22-Jun-2023 15:00:00'}
    {'23-Jun-2023 06:00:00'}
    {'24-Jun-2023 11:00:00'}
    {'25-Jun-2023 19:00:00'}
    {'20-Jun-2023 11:00:00'}
    {'21-Jun-2023 09:00:00'}
    {'23-Jun-2023 12:00:00'}
    {'25-Jun-2023 17:00:00'}
    {'23-Jun-2023 12:00:00'}
    {'22-Jun-2023 07:00:00'}];
% My attempt:
% (1) Get datetime from cells
b = datetime(a,'InputFormat','dd-MMM-yyyy HH:mm:ss');
% (2) Get unique dates
[~, inds] = unique(datestr(b, 'yyyymmdd'), 'rows', 'stable');
uniqueDates = sort(b(inds))
uniqueDates = 7×1 datetime array
   19-Jun-2023 16:00:00
   20-Jun-2023 10:00:00
   21-Jun-2023 10:00:00
   22-Jun-2023 09:00:00
   23-Jun-2023 19:00:00
   24-Jun-2023 16:00:00
   25-Jun-2023 19:00:00
% (3) Count occurences for each date
occurences = groupsummary(table(b),1)
occurences = 18×2 table
bGroupCount______________________________

    19-Jun-2023 16:00:00        1     
    19-Jun-2023 17:00:00        1     
    20-Jun-2023 10:00:00        1     
    20-Jun-2023 11:00:00        2     
    21-Jun-2023 09:00:00        1     
    21-Jun-2023 10:00:00        1     
    21-Jun-2023 17:00:00        1     
    22-Jun-2023 07:00:00        1     
    22-Jun-2023 09:00:00        2     
    22-Jun-2023 15:00:00        1     
    23-Jun-2023 06:00:00        1     
    23-Jun-2023 12:00:00        2     
    23-Jun-2023 14:00:00        1     
    23-Jun-2023 19:00:00        1     
    24-Jun-2023 11:00:00        2     
    24-Jun-2023 16:00:00        1     
% Desired Output
uniqueDates = 
   19-Jun-2023 
   20-Jun-2023 
   21-Jun-2023 
   22-Jun-2023 
   23-Jun-2023 
   24-Jun-2023 
   25-Jun-2023 
   
occurences = 
   19-Jun-2023  2
   20-Jun-2023  3
   21-Jun-2023  3
   22-Jun-2023  4
   23-Jun-2023  5
   24-Jun-2023  3
   25-Jun-2023  2

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Answer 1

Sim 2023-6-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1982764-how-to-find-i-unique-datetimes-and-ii-count-their-occurences#answer_1255394

在 MATLAB Online 中打开

I might have found a solution/workaround, but if there are more compact, correct and robust methods I will accept them!

a = [{'22-Jun-2023 09:00:00'}
    {'23-Jun-2023 19:00:00'}
    {'24-Jun-2023 16:00:00'}
    {'24-Jun-2023 11:00:00'}
    {'19-Jun-2023 16:00:00'}
    {'20-Jun-2023 10:00:00'}
    {'21-Jun-2023 10:00:00'}
    {'22-Jun-2023 09:00:00'}
    {'23-Jun-2023 14:00:00'}
    {'19-Jun-2023 17:00:00'}
    {'20-Jun-2023 11:00:00'}
    {'21-Jun-2023 17:00:00'}
    {'22-Jun-2023 15:00:00'}
    {'23-Jun-2023 06:00:00'}
    {'24-Jun-2023 11:00:00'}
    {'25-Jun-2023 19:00:00'}
    {'20-Jun-2023 11:00:00'}
    {'21-Jun-2023 09:00:00'}
    {'23-Jun-2023 12:00:00'}
    {'25-Jun-2023 17:00:00'}
    {'23-Jun-2023 12:00:00'}
    {'22-Jun-2023 07:00:00'}];
% Get datetime from cells
b = datetime(a,'InputFormat','dd-MMM-yyyy HH:mm:ss','Format','dd-MMM-yyyy');
c = dateshift(b, 'start', 'day');
% Get unique dates
[~, inds] = unique(datestr(c, 'yyyymmdd'), 'rows', 'stable');
uniqueDates = sort(c(inds))
uniqueDates = 7×1 datetime array
   19-Jun-2023
   20-Jun-2023
   21-Jun-2023
   22-Jun-2023
   23-Jun-2023
   24-Jun-2023
   25-Jun-2023
% Count occurences for each date
d = groupsummary(table(c),1)
d = 7×2 table
         c         GroupCount
    ___________    __________

    19-Jun-2023        2     
    20-Jun-2023        3     
    21-Jun-2023        3     
    22-Jun-2023        4     
    23-Jun-2023        5     
    24-Jun-2023        3     
    25-Jun-2023        2     