MATLAB: How to access a field of a struct by indexing

fieldindexingstruct

I have a 1-by-1 struct that possesses 3 fields named B, C, and D. Is there any way to call D by its index (i.e., D is the third field of struct A, so call the third field of struct A without mentioning the field name D) rather than its name (i.e, A.D)?

A.B = 1;
A.C = 2;
A.D = 3;

Best Answer

A_cell = struct2cell(A);
D      = A_cell{3}

Keep in mind that the order of the fields of structs is not necessarily constant:

A.B = 1;
A.C = 2;
A.D = 3;
B.B = 1;
B.D = 3;
B.C = 2;
isequal(A, B)   % >> TRUE!

Related Solutions

MATLAB: How to index every field of a structure and reassign to a structure with a single element in each field

A.b = [1:10];
A.c = [2:11];
A.d = [3:12];
a= A ;
for f=fieldnames(a)'
    a.(f{1})(2:end)=[]; 
end

MATLAB: Is there a way to extract specific fields from a structure

Solution

>> S.a = 'Hello';
>> S.b = 'World';
>> C = {'a','b'};
>> D = cellfun(@(f)getfield(S,f),C,'UniformOutput',false);
>> horzcat(D{:})
ans = HelloWorld

Take a look at fieldnames.

Improvement

Note that if the fieldnames really are numbered like that then a much better solution would be to consider using a non-scalar array. A non-scalar structure is a much better way to store data, compared to numbered fieldnames. Using a non-scalar structure would avoid having to perform slow and complicated tricks like this, instead you could use the neat and fast methods shown in the link:

>> S(1).f = 'Hello';
>> S(2).f = 'World';
>> [S.f]
ans = HelloWorld

See how choosing the best data storage makes a huge difference to the quality of code!

Best Answer

Related Solutions

MATLAB: How to index every field of a structure and reassign to a structure with a single element in each field

MATLAB: Is there a way to extract specific fields from a structure

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