How can I assign values to a Structure with multiple subfields with one line of code?

Question

Mete Soylu 2022-4-5

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评论： Stephen23 2022-4-5

% Hi I want to assign values with different sizes to a structure with subfields respectively. However I want to do it with one line of code due to running speed issues.
% I will try to write the code as simple as possible. Lets say I have a structure with 4 subfields
ExampleStruct.SubField1 = [];
ExampleStruct.SubField2 = [];
ExampleStruct.SubField3 = [];
ExampleStruct.SubField4 = [];
% Now I will create a cell array with 4 cells
CellArr = {[1,2,3,4], [1:10], ['Man of Numenor'], ['Matlab is Great']};
% I can make it with for loop like this 
FieldNames = fieldnames(ExampleStruct);
for i=1:length(FieldNames)
    ExampleStruct.(FieldNames{i}) = CellArr{i};
end
% But I dont want to do it, because for this code time consuming is large when subfield numbers are 1000 or more.
% How can I make what this for loop does in one line of code ? 
% I tried arrayfun and similar approaches with the function handle @(x) that I created, but I couldn't find the answer.
% Could you please help me? I would be very appreciated

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Stephen23 2022-4-5

I doubt that you will find a more efficient approach than using a FOR-loop.

The approach not robust: consider that fieldnames are ordered, then if their order changes the wrong data will get allocated from the cell array. It is a bit smelly: https://en.wikipedia.org/wiki/Code_smell

Note that if you used a non-scalar structure with one field it could be easily achieved using a comma-separated list.

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Answer 1

Jan 2022-4-5

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编辑：Jan 2022-4-5

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You mention "as simple as possible". Then avoid unneeded operators e.g. by replaing:

CellArr = {[1,2,3,4], [1:10], ['Man of Numenor'], ['Matlab is Great']};

by

CellArr = {[1,2,3,4], 1:10, 'Man of Numenor', 'Matlab is Great'};

[] is Matlab operator for the concatenatoin of arrays. 1:10 is a vector already and [1:10] concatenates it with nothing. This is a wate of time only.

This is the compact way:

Fields  = {'SubField1', 'SubField2', 'SubField3', 'SubField4'};
CellArr = {[1,2,3,4], 1:10, 'Man of Numenor', 'Matlab is Great'};
ExampleStruct = cell2struct(CellArr(:), Fields(:));

"1000 subfields" sounds like a bad design. Can you keep the overview over typos in such a huge struct?

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Answer 2

Bruno Luong 2022-4-5

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编辑：Bruno Luong 2022-4-5

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Not sure about your claim of one statement is faster than for loop. Whatever here is oneline code

Exampe = struct()
Exampe = struct with no fields.
[ExampleStruct.SubField1 ExampleStruct.SubField2 ExampleStruct.SubField3 ExampleStruct.SubField4] = deal([]);
ExampleStruct
ExampleStruct = struct with fields:
    SubField1: []
    SubField2: []
    SubField3: []
    SubField4: []