How do structures work?
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Hi there. Say that I use an array of structures and that then I want to create an array like:
[ss.phi] % ss is the array of structures, and phi a number
Now, the above works just fine but what does not work is:
[ss.phi(1)] % this time phi is an array of doubles and I only want to keep the first element
Why is the last case wrong? And how to fix it?
Thanks. Chiara
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Answers (2)
Jarrod Rivituso
on 13 Apr 2011
I think MATLAB doesn't let you nest subscripts like that. However, there are workarounds. Is this what you are looking for:
>> var(1).a = [3 4];
>> var(2).a = [5 6];
>> var(1).b = 10;
>> var(2).b = 13;
>> getFirstElementFcn = @(x) x(1);
>> allFieldsA = {var.a};
>> cellfun(getFirstElementFcn, allFieldsA)
1 Comment
Jarrod Rivituso
on 13 Apr 2011
Note that I've created an anonymous function to go through and grab the first element, and then I've put all the field values in a structure array, and then finally I apply the function to the field values within the cell.
Oleg Komarov
on 13 Apr 2011
ss.phi = rand(10);
ss.phi = ss.phi(1)
Saying it's not working is as far as you can get from a clear description of a problem.
EDIT Following Jarrod's interpretation (which by the way, I now think, is your situation), another way:
var(1).a = [1 2; 3 4];
var(2).a = [5 6; 7 8];
temp = cat(3,var.a);
squeeze(temp(1,1,:))
Or fetching elements in a loop (no vectorized way available):
% Preallocate
...
for s = 1:numel(var)
out(...) = var(s).a(1)
end
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