Create and populate field on existing structure. Impossible?

Question

MrGrady 2013-9-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/87168-create-and-populate-field-on-existing-structure-impossible

编辑： Stephen23 2023-6-17

采纳的回答： Arthur

在 MATLAB Online 中打开

Hi all,

I have created a structure and populated it with data from a cell array:

MyStruct=struct('Field1',num2cell(DFullData{1,1}),'Field2',num2cell(DFullData{1,2}))

Fabulous:

MyStruct = 
1x461 struct array with fields:
      Field1
      Field2

Note that

>> MyStruct(1)
ans = 
      Field1: 7.354373336826041e+05
      Field2: 2.407360200100000e+10
>> MyStruct(2)
ans = 
      Field1: 7.354373336883913e+05
      Field2: 2.319540190100000e+10

How on earth do I create a Field3 and populate it like above (obviously without using a loop)?

Everything I tried ("setfield" and every permutation of squared and curly brackets!) populates only the first element with the whole cell array.

>> MyStruct().Field3=num2cell(DFullData{1,5})
>> MyStruct(1)
ans = 
      Field1: 7.354373336826041e+05
      Field2: 2.407360200100000e+10
      Field3: {1x461 cell}
>> MyStruct(2)
ans = 
      Field1: 7.354373336883913e+05
      Field2: 2.319540190100000e+10
      Field3: []

What is the correct syntax to populate each element of Field3 with each element of the cell array? Thanks!

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Answer 1

Arthur 2013-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/87168-create-and-populate-field-on-existing-structure-impossible#answer_96705

在 MATLAB Online 中打开

Did you try this?

[MyStruct.Field3] = DFullData{:,5};

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Stephen23 2023-6-17

编辑：Stephen23 2023-6-17

+1 How it works:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

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Answer 2

Azzi Abdelmalek 2013-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/87168-create-and-populate-field-on-existing-structure-impossible#answer_96685

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n=numel(DFullData{1,5})
for k=1:n
  MyStruct(k).Field3=DFullData{1,5}(k)
end

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Answer 3

Azzi Abdelmalek 2013-9-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/87168-create-and-populate-field-on-existing-structure-impossible#answer_96712

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f=fieldnames(MyStruct)
g=struct2cell(MyStruct)
[n,m]=size(g)
g(n+1,1:m)=num2cell(DFullData{:,5})
MyStruct=cell2struct(g,[f;{'field3'}])

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MrGrady 2013-9-16

Thank you very much, this is a bit convoluted but does the job! I am surprised that we have to go to such lenghts to perform such a simple operation, you'd think Mathworks would have thought about it. Oh well... Thanks again :)

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