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

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

% 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
             b              GroupCount
    ____________________    __________

    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

Answer 1

[Sim]

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