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Removing close datetimes from datetime array

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Dylan den Hartog
Dylan den Hartog on 14 May 2020
Commented: Campion Loong on 22 May 2020
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
Sindar on 15 May 2020
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
Campion Loong on 22 May 2020
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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Answers (1)

Jalaj Gambhir
Jalaj Gambhir on 18 May 2020
Edited: Jalaj Gambhir on 18 May 2020
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));
Hope this helps!

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