how know size of field struct

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piero on 5 Jun 2023
Commented: piero on 5 Jun 2023
Sis is a struct
D is a field of struct
>> size(Sis.D)
Error using size

Accepted Answer

Walter Roberson
Walter Roberson on 5 Jun 2023
What you failed to indicate is that Sis is a non-scalar struct. Sis.D is then "struct expansion". So
is the same as if you had written
size(Sis(1).D, Sis(2).D, Sis(3).D, Sis(4).D, up to Sis(63).D)) %or whatever the size of Sis is
You can inquire about size(Sis(1).D) or size(Sis(end).D) or as appropriate.
If you need to know the size of each of the Sis.D entries then
SisSizes = arrayfun(@(S) size(S.D), Sis, 'uniform', 0);
If all of the Sis.D entries had the same dimension then you could also proceed to
SisSizeArray = cell2mat(SisSizes(:));
which would be a numeric array with numel(Sis) rows and numdim(Sis(1).D) columns

More Answers (1)

the cyclist
the cyclist on 5 Jun 2023
That command will give an error for some values of Sis.D, and not for others. Regardless, I don't think it will do what you expect. For example, what do you think size(Sis.D) should give for the following struct?
Sis(1).D = [1 2];
Sis(2).D = [1 2 3];
Sis(3).D = [1; 2; 3];
Perhaps you should upload your data, and explain what you are trying to do.
  1 Comment
piero on 5 Jun 2023
ok ..i understand
the .D have same length in all field in struct

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