MATLAB: Assign value to field of nested structure in a structure array

assign value to field of all elementsMATLABnested structurestructure array

Hello, I will use a simple example to show what I am after. I have a structure array 'person' with fields ('First_Name' , 'Last_Name' , 'FamilyInfo'), where 'FamilyInfo' is a structure with three fields ('FatherName' , 'MotherName' , 'NumberOfSiblings').
I create 4 elements in person structure array and fill all the 'First_Name' and 'Last_Name' fields but the 'FamilyInfo' field is left empty. Now, for all the 4 elements in the 'person' structure array, I want to assign at once the same value to the field "NumberOfsiblings" in the nested structure 'Family', but MATLAB throws an error. Here is the code;
Create an empty structre array
person = struct('First_Name',[],'Last_Name',[],...
'FamilyInfo',struct('FatherName',[],'MotherName',[],'NumberOfsiblings',[]));
Create elements in the array but the Family field is left empty
FirstNames = {'Joe','Jack','William','Averel'};
[person(1:4).First_Name]=deal(FirstNames{:});
[person(1:4).Last_Name]=deal('Dalton');
For all the elements in person structure array, assign the same value (3) to the NumberOfsiblings field, of the Family field.
[person(1:4).FamilyInfo.NumerOfsiblings] = 3;
Error message pops up;
Expected one output from a curly brace or dot indexing expression, but there were 4 results.
Is there a way to do it without using a for loop? One-line code is preferred. Thanks

Best Answer

That's one of the downside of multilevel structures. As Jan says, it's not possible to assign at once to fields of a substructure.
More importantly, note that when you grow the root source structure (by adding the first names of the 4 persons, only the 1st element of the structure array is a FamilyInfo substructure. The other 3 are initialised empty, because matlab does not copy the type of fields when it grows structure arrays. So if you actually want to have the correct FamilyInfo substructure after growing, you actually need to deal a FamilyInfo field to each element. You may as well set the value of NumberOfSiblings to the correct one:
[person.FamilyInfo] = deal(struct('FatherName',[],'MotherName',[],'NumberOfsiblings',3);
Note that if you want to avoid losing the FamilyInfo struct, don't grow the array but initialise it at the correct size to start with:
numpersons = 4;
person = struct('First_Name',[],'Last_Name',[],...
'FamilyInfo',repmat({struct('FatherName',[],'MotherName',[],'NumberOfsiblings',[])}, 1, numpersons));
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