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create an array of single struct

Asked by Aditya Jain on 9 Nov 2015
Latest activity Commented on by Guillaume
on 9 Nov 2015
structElement = struct('a1','', 'a2', '', 'a3', '', 'a4', '');
s1 = repmat(structElement, [1,1]);
The above code gives a 1x1 struct
s2 = repmat(structElement, [2,1]);
The above code results in a 2x1 struct
If I do s2(1) it returns a struct
If I do s1(1) it returns a1.
How can I create s1, such that s1(1) will give me back a struct. Basically I want to create an array of single struct.

  2 Comments

Both those syntaxes return the full struct. They do in Matlab R2015b that I am using.
s1 = structElement;
would do though. The repmat instruction is redundant.
I'm fairly certain they've done so in every version of matlab (barring any bug).
It would never make any sense for an index to return a field of a structure. Particularly since everything in matlab, including scalar structures, is always an array.

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1 Answer

Answer by Guillaume
on 9 Nov 2015
 Accepted Answer

"If I do s1(1) it returns a1." No, it also returns a structure.
Both s1 and structElement are arrays of a single struct:
>>s1(1)
ans =
a1: ''
a2: ''
a3: ''
a4: ''
>>size(s1)
ans =
1 1
>>size(structElement)
ans =
1 1
Everything in matlab is an array. Scalars (numbers, structs, objects, etc.) are stored as array of size 1x1

  3 Comments

My bad. You are right. Is there a way I can create a cell array of structs instead of normal matrix?
s2 = repmat({structElement}, [2,1]);
You can create cell arrays of structures the same way you create cell arrays of numbers, by plain assignment, using arrayfun / cellfun, using num2cell, etc.
s = struct('a', {1 2 3 4 5}, 'b', ''); %creates a 1x5 array of struct
c = num2cell(s); %convert matrix to cell array
Another way:
s = struct('a', '', 'b', '');
c = cell(2, 5);
c(:) = {s};
However, if all the structures have the same fields, I don't see the point of storing them in a cell array.

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