Create an array of empty durations

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Christian Breinholt
Christian Breinholt 2017-11-21
评论： Karol Ondrejkovic 2022-6-17
Is there a way to create an array of durations similar to the way I can create an array of strings, zeroes etc. i.e.
str = strings(size, 0)
i tried something like
dur = durations(size, 0)
but that does not work.

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采纳的回答

Walter Roberson
Walter Roberson 2017-11-21
编辑：Walter Roberson 2017-11-21
duration(nan(NumberOfEntries,3))
If you want a 2D array of durations then you would probably need to reshape() the above.
Alternately you could use
NaT(numrows, numcols) - NaT(1)
to get a numrows x numcols duration array.
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Raphaël Nussbaumer
Raphaël Nussbaumer 2021-4-21
Look like the second method is not working anymore with R2020b at least...
For instance
tmp = NaT(1,2)
tmp(1)=duration(0,0,1)
returns:
Error using datetime/parenAssign (line 66)
Right hand side of an assignment must be a datetime array or text representing dates and times.
Stephen23
Stephen23 2021-4-21
编辑：Stephen23 2021-4-21
Ran in:
tmp is a datetime array. The output of duration is a duration array.
What do you expect to occur when you allocate a duration to a datetime array? What date is "five minutes" ?
"Look like the second method is not working anymore with R2020b at least... "
It works when I try it:
X = NaT(2,3)-NaT(1)
X = 2×3 duration array
NaN NaN NaN NaN NaN NaN

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更多回答（2 个）

Jan
Jan 2017-11-21
I asssume that https://www.mathworks.com/help/matlab/ref/nat.html: "Not-a-Time" does not help directly. What about:
duration(NaN(size));
Steven Lord
Steven Lord 2021-4-21
Ran in:
Another way to create an empty array of duration objects is to use the empty function for the class.
d = duration.empty(5, 0)
d = 5×0 empty duration array
  2 个评论
Raphaël Nussbaumer
Raphaël Nussbaumer 2021-4-21
Nice one! Much better. It would be nice to be able to do:
duration.empty(size(X))
with X another matrix od any size.
Thanks anyway!
Steven Lord
Steven Lord 2021-4-21
Ran in:
As long as X is empty you can.
X = zeros(1, 2, 3, 4, 0);
D = duration.empty(size(X));
size(D)
ans = 1×5
1 2 3 4 0
An empty array in MATLAB must have the size in at least one dimension equal to 0 (as per the documentation for the isempty function) so something like this wouldn't work as the error message clearly states.
X = 1:10;
D = duration.empty(size(X))
Error using duration.empty (line 1095)
At least one dimension must be zero.

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