Copy of one field of a structured array

Question

John Petersen 2013-3-12

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https://ww2.mathworks.cn/matlabcentral/answers/66913-copy-of-one-field-of-a-structured-array

Is there a way to make a copy of one field of a structured array without doing a loop? I have tried but it just results in the first element.

Creation of sample structure

for i=1:5
    A(i).A = i; 
    A(i).B = i+10;
end
>>C = A.B
C = 
      11

Likewise

>> C = A(1:3).B
C  =
      11
instead of C(1).B = 11, C(2).B = 12, and C(3).B = 13 like I want.

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Answer 1

per isakson 2013-3-12

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编辑：per isakson 2013-3-12

在 MATLAB Online 中打开

One way to do it:

    >> C = cell2struct( num2cell([A.B]), {'B'} )
    C = 
    5x1 struct array with fields:
        B
    >> C(1).B
    ans =
        11
    >> C(2).B
    ans =
        12

another

    >> C = struct( 'B',  num2cell([A.B]) )
    C = 
    1x5 struct array with fields:
        B
    >> C(1).B
    ans =
        11
    >> C(2).B
    ans =
        12
    >>

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John Petersen 2013-3-12

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Answer 2

the cyclist 2013-3-12

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https://ww2.mathworks.cn/matlabcentral/answers/66913-copy-of-one-field-of-a-structured-array#answer_78377

编辑：the cyclist 2013-3-12

在 MATLAB Online 中打开

Yet another way:

[C(1:numel(A)).B] = A.B;

Note that this method will not overwrite other fields of C, if they exist. Some of the methods in other answers will, so be cautious!

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per isakson 2013-3-12

编辑：per isakson 2013-3-12

The two functions, struct and cell2struct, create a new struct and overwrite an existing C.

I'll try to remember that numel(A) in the rhs-expression creates a new struct if C does not exist. And I'll reread the entry on deal in the documentation.

John Petersen 2013-3-13