Preallocating a structure with a changing number of rows within a field

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Christoper Angelo Malayan
评论： Bruno Luong 2021-1-10
Hi all. I'm relatively new in MATLAB and I'm trying to optimize my code.
I have this function:
function G = GroupM1(A,num_K)
%Grouping r according to m1 and arranging from high to low
for i = [1:num_K]
G(i).dist = A(A.m1 == i,:);
G(i).dist = sortrows(G(i).dist, string(i),'ascend');
end
end
It produces a structure 'G' (see attached file)
'A' is just a 100x17 table. And In this case, num_K == 9. The number of rows in structure 'G' is always equal to num_K.
My questions is:
How can I preallocate this structure 'G' that has 1 field (.dist) containing different sized tables so that the row number is always equal to num_K?
Any help is appreciated. Thank you.

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采纳的回答

Bruno Luong
Bruno Luong 2021-1-9
There is no need to preallocate a field (or in fact any variable) if you don't grow the array itself in a loop, which is your case.
  2 个评论
Christoper Angelo Malayan
Christoper Angelo Malayan 2021-1-10
Hi Bruno. Thanks for answering.
But the table sizes within the fixed structure 'G' is changing and MATLAB advices me to preallocate it i.e. the rows of struct G.dist is always == to num_K but the dimension of the table G(n).dist will change every iteration.
Any tips on how to preallocate these tables within the struct?
Thanks
Bruno Luong
Bruno Luong 2021-1-10
I though you want to prealloacate the fields.
If you want to preallocate the structure array G do this before the loop
G = struct('dist',cell(1,num_K));

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