Removing close datetimes from datetime array

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Dylan den Hartog 2020-5-14

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https://ww2.mathworks.cn/matlabcentral/answers/525476-removing-close-datetimes-from-datetime-array

评论： Campion Loong 2020-5-22

I have this 5x1 datetime array:

   14-May-2020 10:47:18
   14-May-2020 10:47:19
   14-May-2020 10:47:20
   14-May-2020 10:53:36
   14-May-2020 10:54:05

I want to remove all datetimes within 2 seconds of another datetime, so in this case I want to remove the second and third datetime '14-May-2020 10:47:19' and '14-May-2020 10:47:20' and keep '14-May-2020 10:47:18'. Is there an easy way to do this?

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Sindar 2020-5-15

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diff will allow you determine the difference between times, but you haven't fully specified the problem, and some versions are significantly easier. Let's consider this example:

   14-May-2020 10:47:18
   14-May-2020 10:47:19
   14-May-2020 10:47:20
   14-May-2020 10:47:21
   14-May-2020 10:53:36
   14-May-2020 10:54:05

What remains based on various rules:

"remove all datetimes within 2 seconds of another datetime"

   14-May-2020 10:53:36
   14-May-2020 10:54:05

"remove all datetimes within 2 seconds of the previous datetime"

   14-May-2020 10:47:18
   14-May-2020 10:53:36
   14-May-2020 10:54:05

"remove datetimes -- starting from the beginning -- so that none are within 2 seconds of each other"

   14-May-2020 10:47:18
   14-May-2020 10:47:21
   14-May-2020 10:53:36
   14-May-2020 10:54:05

Which one would you like?

Campion Loong 2020-5-22

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If I may take a guess that Sindar's second example (i.e. "remove all datetimes within 2 seconds of the previous datetime") is the desired outcome, I'd do:

>> dt = sort(dt);
>> dt([true; diff(dt) >= seconds(2)]) % the leading TRUE accounts for the first element offset

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Answer 1

Jalaj Gambhir 2020-5-18

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https://ww2.mathworks.cn/matlabcentral/answers/525476-removing-close-datetimes-from-datetime-array#answer_433059

编辑：Jalaj Gambhir 2020-5-18

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Hi,

The following is one of the way in which you can achieve your task, as pointed out in the comment, "remove all datetimes within 2 seconds of the previous datetime"

DateStrings = {'14-May-2020 10:47:18','14-May-2020 10:47:19','14-May-2020 10:47:20','14-May-2020 10:53:36','14-May-2020 10:54:05', '14-May-2020 10:51:03', '14-May-2020 10:51:05'};
t = datetime(DateStrings,'InputFormat','dd-MMM-yyyy HH:mm:ss');
t = sort(t);
for i=1:length(t)
    if ~isnat(t(i))
        lower = t(i)+seconds(1);
        upper = lower + seconds(2);
        t(isbetween(t,lower,upper)) = NaT;
    end
end
result = t(~isnat(t));