Create an array of empty durations

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.

Answer 1

[Walter Roberson]

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.

[Christian Breinholt]

Yes, that works! Thank you both!

[Raphaël Nussbaumer]

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]

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

Answer 2

[Jan]

I asssume that https://www.mathworks.com/help/matlab/ref/nat.html: "Not-a-Time" does not help directly. What about:

duration(NaN(size));

[Karol Ondrejkovic]

For me duration(strings(size)) works well.

Example:

duration(strings([2,3]))

Answer 3

[Steven Lord]

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

[Raphaël Nussbaumer]

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]

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.