Array of Structures to Structure of arrays

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Andrew C 2021-9-30

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回答： Chunru 2021-10-1

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Referencing this video Array of Structures vs. Structures of Arrays - Video - MATLAB (mathworks.com)

How can I convert an array of structures into a structure of arrays.

I currently have an array of structs of size N that the only way to access it is to call them by

var = struct(1).fieldname

Where the fieldname is referencing a array of 1xM.

When I try to call var = struct.fieldname or var = struct(:).fieldname I only get one value, while I would like to get all values.

I have tried to do struct2cell and cell2mat, but these options expand the nested array.

What I want is to call each fieldname and get a matrix of NxM.

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Jan 2021-9-30

编辑：Jan 2021-9-30

The question is not clear yet, because the readers cannot know, how your struct looks like.

Andrew C 2021-9-30

Apologies. I will try to make it a bit clearer

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Answer 1

Sulaymon Eshkabilov 2021-10-1

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Jan is right that your questions are not quite clear for the reader as described here. But what I've understood is the following:

% Let's say that X is the structure array:
FNames = fieldnames(X);                   % ALL Field Names residing in X structure array can be obtained
% This part seems to be optional for your exercise:
XX=zeros(length(FNames), 1);
for ii = 1:length(FNames)
xi = getfield(X, FNames{ii});             %  Field Values 
XX(ii) = xi;
end

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Answer 2

Chunru 2021-10-1

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% array of structure
M = 5;
for i=1:M
    a(i).f1 = rand(1,1);
    a(i).f2 = rand(1,1);
end
a
a = 1×5 struct array with fields:
    f1
    f2
a(1)
ans = struct with fields:
    f1: 0.6493
    f2: 0.9459
% struncrure of array [assuming each field is a scalar in a]
f = fields(a(1));
for i=1:length(f)
    b.(f{i}) = [a.(f{i})];
end
b
b = struct with fields:
    f1: [0.6493 0.7285 0.1068 0.3718 0.3805]
    f2: [0.9459 0.5456 0.5360 0.2124 0.6030]