Automatically creating and editing Fields of struct with for Loop

Question

ga56 2016-12-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/317276-automatically-creating-and-editing-fields-of-struct-with-for-loop

评论： ga56 2016-12-18

That is my current code:

%%Struct Problem
for k=1:5 
    struct.i(k).m=rand;
    struct.i(k).n=rand;
    struct.i(k).o=rand;
    struct.i(k).p=rand;
    struct.i(k).q=rand;
end

And I want to automate the steps in a way like this:

for k=1:5 
    for a=['m','n','o','p','q']
    struct.i(k).a=rand;
    end
end

How can I automatically create and edit fields with a for loop?

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Stephen23 2016-12-17

Dynamic fieldnames are explained in the documentation:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

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Answer 1

Image Analyst 2016-12-17

2
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https://ww2.mathworks.cn/matlabcentral/answers/317276-automatically-creating-and-editing-fields-of-struct-with-for-loop#answer_247619

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What's wrong with the first way? That's the method I'd prefer. It's much more straightforward and intuitive and easy to understand than using dynamic field names.

I really don't recommend dynamic field names, but if you insist, it is possible, though a lot more complicated than your first method:

% Initialize just one struct with 5 fields.
s = struct('m',0, 'n',0, 'o',0, 'p',0, 'q',0)
letters = {'m', 'n' 'o','p','q'}
size(s)
% Now make an array of 10 of them.
myStruct = repmat(s, 1, 10) % Whatever
size(myStruct)
for k = 1 : size(myStruct, 2)
  for lIndex = 1 : length(letters)
    fprintf('Assigning field %s to structure #%d\n', letters{lIndex}, k)
    myStruct(k).(letters{lIndex}) = rand;
  end
end