Datetimes don't seem to be recognised

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Louise Wilson 2021-11-10

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评论： Steven Lord 2021-11-10

Can anyone explain to me why this isn't working? For some reason, the datetime t is not recognised as occurring between times.t1.start and times.t1.end, even though it DOES! It is recognised as occurring after t1.start, but not before t1.end.

isbetween() also does not work so I am guessing I have overlooked something simple...

start=datetime(2021,08,11,09,58,25); 
last=datetime(2021,08,11,10,01,00); 
t=gps.DateTime(ii) %reading same datetime from my table
t=datetime(2021,08,11,09,59,25)
%if vessel position time occurs during particular transect working on
if (t>=start)&&(t<last)
    
    %append it to specific part of structure
    disp('It works!')
    
else
    disp('It does not work')
end
%Datetime from my table:
t = 
  datetime
   11-Aug-2021 09:59:25
   
%Datetime datetime(2021,08,11,09,59,25)
t = 
  datetime
   11-Aug-2021 09:59:25

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采纳的回答

Star Strider 2021-11-10

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I’m not certain what you’re doing and I can’t run the posted code. I’m also not certain what the actual problem is.

See if the isbetween function will do what you want with respect to the if block.

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Star Strider 2021-11-10

编辑：Star Strider 2021-11-10

在 MATLAB Online 中打开

Well, they¹re definitely datetime values. So much for that theory!

I used this code —

LD = load('Louise Wilson subset.mat');
subset = LD.subset;
start=datetime(2021,08,11,09,58,25); 
last=datetime(2021,08,11,10,01,00); 
TF = isbetween(subset.DateTime, start, last)

to get this result —

TF =

5×1 logical array

So if it’s any consolation, none of them meet the criteria.

I still can’t follow the code so I’m not certain what you’re doing, however this may be part of the problem, if these are the dates and times being compared. Nothing is actually wrong, it’s just that the dates in ‘subset.DateTime’ aren’t in the interval being tested. That may not be true for all values of a larger datetime array, however it’s true for this set.

EDIT —

The problem is that the format is different between the two sets of datetime arrays —

start.Format = dt.Format

produces —

start =

datetime

08/11/2021 09:58:25

so the days and months are reversed between the different values. The ‘subset.DateTime’ format is 'MM/dd/uuuu HH:mm:ss' and the ‘start’ and ‘end’ format is 'dd-MMM-uuuu HH:mm:ss' that being the problem. I am not certain which is the desired format so I will not convert them. Nevertheless, they all must be the same, and then the logic will work as intended. Convert them using the approach I used here, supplying the desired format string for both the comparison and ‘subset’ arrays. Then do the comparison.

Louise Wilson 2021-11-10

All good, it works perfectly :-) Thank you. The data I am working with is huge and a lot of time consuming processing has already been done so the fix up solution is preferrable by far!

Steven Lord 2021-11-10

在 MATLAB Online 中打开

If that doesn't work, perhaps the data in the file was more precise than you thought it was.

t1 = datetime(2021, 11, 10, 14, 25, 00)
t1 = datetime
   10-Nov-2021 14:25:00
t2 = datetime(2021, 11, 10, 14, 25, 0.4)
t2 = datetime
   10-Nov-2021 14:25:00
t1 >= t2 % correctly false even though they display the same
ans = logical
   0