How to avoid "NaT" when converting a cell into datetime ? (Or: how to add missing parts of datetime ?)

Question

Sim 2022-8-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1778300-how-to-avoid-nat-when-converting-a-cell-into-datetime-or-how-to-add-missing-parts-of-datetime

编辑： Sim 2022-8-12

采纳的回答： Stephen23

在 MATLAB Online 中打开

How to avoid "NaT" when converting a cell into datetime ?

(Or: how to add missing parts of datetime ?)

a = [
    {'14-Jul-2021 17:00:00'}
    {'15-Jul-2021 12:00:00'}
    {'16-Jul-2021 21:00:00'}
    {'17-Jul-2021'         }
    {'18-Jul-2021 06:00:00'}
    {'19-Jul-2021 04:00:00'}
    {'20-Jul-2021 17:00:00'}
    {'21-Jul-2021 08:00:00'}]
a = 8×1 cell array
    {'14-Jul-2021 17:00:00'}
    {'15-Jul-2021 12:00:00'}
    {'16-Jul-2021 21:00:00'}
    {'17-Jul-2021'         }
    {'18-Jul-2021 06:00:00'}
    {'19-Jul-2021 04:00:00'}
    {'20-Jul-2021 17:00:00'}
    {'21-Jul-2021 08:00:00'}
datetime(a)
ans = 8×1 datetime array
   14-Jul-2021 17:00:00
   15-Jul-2021 12:00:00
   16-Jul-2021 21:00:00
   NaT                 
   18-Jul-2021 06:00:00
   19-Jul-2021 04:00:00
   20-Jul-2021 17:00:00
   21-Jul-2021 08:00:00

As workaround, how to add a representative hour (e.g. '12:00:00') where it is missing, in order to avoid a "NaT" ?

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Answer 1

Stephen23 2022-8-12

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https://ww2.mathworks.cn/matlabcentral/answers/1778300-how-to-avoid-nat-when-converting-a-cell-into-datetime-or-how-to-add-missing-parts-of-datetime#answer_1025430

编辑：Stephen23 2022-8-12

在 MATLAB Online 中打开

"How to avoid "NaT" when converting a cell into datetime ?"

Convert each cell individually. Certainly not as efficient as one DATETIME call, but it is fairly simple:

C = {...
    '14-Jul-2021 17:00:00'
    '15-Jul-2021 12:00:00'
    '16-Jul-2021 21:00:00'
    '17-Jul-2021'
    '18-Jul-2021 06:00:00'
    '19-Jul-2021 04:00:00'
    '20-Jul-2021 17:00:00'
    '21-Jul-2021 08:00:00'}; % one cell array :)
D = cellfun(@datetime,C)
D = 8×1 datetime array
   14-Jul-2021 17:00:00
   15-Jul-2021 12:00:00
   16-Jul-2021 21:00:00
   17-Jul-2021 00:00:00
   18-Jul-2021 06:00:00
   19-Jul-2021 04:00:00
   20-Jul-2021 17:00:00
   21-Jul-2021 08:00:00

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Stephen23 2022-8-12

在 MATLAB Online 中打开

"but the thing is that the position can change"

Of course, you can use any indexing you want, you are not restricted to just using index 4. For example, if you want to detect all character vectors shorter than 12 characters and add 12 hours to the corresponding datetime:

C = {...
    '14-Jul-2021 17:00:00'
    '15-Jul-2021 12:00:00'
    '16-Jul-2021 21:00:00'
    '17-Jul-2021'
    '18-Jul-2021 06:00:00'
    '19-Jul-2021 04:00:00'
    '20-Jul-2021 17:00:00'
    '21-Jul-2021 08:00:00'}; % one cell array :)
D = cellfun(@datetime,C);
X = cellfun(@numel,C)<12; % or whatever logic you want to use (which you did not explain)
D(X) = D(X) + hours(12)
D = 8×1 datetime array
   14-Jul-2021 17:00:00
   15-Jul-2021 12:00:00
   16-Jul-2021 21:00:00
   17-Jul-2021 12:00:00
   18-Jul-2021 06:00:00
   19-Jul-2021 04:00:00
   20-Jul-2021 17:00:00
   21-Jul-2021 08:00:00

Sim 2022-8-12

编辑：Sim 2022-8-12

Cool, thanks!! :-)

The logic of indexing the missing parts of datetime elements by using the "characters length of those datetime elements" (i.e. 11 characters in '17-Jul-2021'), works well in my case, many thanks !

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